Method and apparatus for receiving a synchronization signal

ABSTRACT

The present invention discloses a method for a terminal to receive a synchronization signal in a wireless communication system. Particularly, the method includes the steps of receiving a synchronization block including a primary synchronization signal (PSS), a secondary synchronization signal (SSS), and a physical broadcasting channel (PBCH) and receiving a DMRS (demodulation reference signal) via resource region in which the PBCH is received. In this case, an index of the synchronization block can be determined in consideration of a sequence of the DMRS.

TECHNICAL FIELD

The present invention relates to a method of receiving a synchronizationsignal and an apparatus therefor, and more particularly, to a method ofdetermining an index of a synchronization signal received by a UE and anapparatus therefor.

BACKGROUND ART

As more communication devices require greater communication traffic,necessity for a next generation 5G system corresponding to mobilebroadband communication, which is enhanced compared to a legacy LTEsystem, is emerging. In the next generation 5G system, scenarios can beclassified into Enhanced Mobile BroadBand (eMBB), Ultra-reliableMachine-Type Communications (uMTC), Massive Machine-Type Communications(mMTC), and the like.

The eMBB corresponds to a next generation mobile communication scenariohaving such a characteristic as high spectrum efficiency, high userexperienced data rate, high peak data rate, and the like, the uMTCcorresponds to a next generation mobile communication scenario havingsuch a characteristic as ultra-reliable, ultra-low latency, ultra-highavailability, and the like (e.g., V2X, Emergency Service, RemoteControl), and the mMTC corresponds to a next generation mobilecommunication scenario having such a characteristic as low cost, lowenergy, short packet, and massive connectivity (e.g., IoT).

DISCLOSURE OF THE INVENTION Technical Task

An object of the present invention is to provide a method of receiving asynchronization signal and an apparatus therefor.

Technical tasks obtainable from the present invention are non-limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of receiving a synchronization signal block,which is received by a user equipment (UE) in a wireless communicationsystem, includes receiving a synchronization signal block including aprimary synchronization signal (PSS), a secondary synchronization signal(SSS), and a physical broadcasting channel (PBCH), and receiving ademodulation reference signal (DMRS) via a resource region in which thePBCH is received. In this case, an index of the synchronization signalblock can be determined in consideration of a sequence of the DMRS.

In this case, if the number of synchronization signal block candidatescapable of transmitting the synchronization signal block satisfies aspecific value, the index of the synchronization signal block can bedetermined in further consideration of a plurality of bits included in apayload of the PBCH.

And, 3 bits among 6 bits for the index of the synchronization signalblock are received via the DMRS and the remaining 3 bits can be receivedvia the payload of the PBCH.

And, the number of bits for the index of the synchronization signalblock received via the DMRS can be determined according to the number ofsynchronization signal block candidates capable of transmitting thesynchronization signal block.

And, the index of the synchronization signal block may correspond to asingle DMRS index.

And, the sequence of the DMRS can be generated based on a cellidentifier for identifying a cell and the index of the synchronizationsignal block.

And, a part of bits included in a scrambling sequence of the PBCH maycorrespond to the index of the synchronization signal block.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, auser equipment (UE) receiving a synchronization signal block in awireless communication system includes an RF module configured totransceive a signal with a base station (BS) and a processor configuredto receive a synchronization signal block including a primarysynchronization signal (PSS), a secondary synchronization signal (SSS),and a physical broadcasting channel (PBCH) in a manner of beingconnected with the RF module, the processor configured to receive ademodulation reference signal (DMRS) via a resource region in which thePBCH is received. In this case, an index of the synchronization signalblock can be determined in consideration of a sequence of the DMRS.

In this case, if the number of synchronization signal block candidatescapable of transmitting the synchronization signal block satisfies aspecific value, the index of the synchronization signal block can bedetermined in further consideration of a plurality of bits included in apayload of the PBCH.

And, 3 bits among 6 bits for the index of the synchronization signalblock are received via the DMRS and the remaining 3 bits can be receivedvia the payload of the PBCH.

And, the number of bits for the index of the synchronization signalblock received via the DMRS can be determined according to the number ofsynchronization signal block candidates capable of transmitting thesynchronization signal block.

And, the index of the synchronization signal block may correspond to asingle DMRS index.

And, the sequence of the DMRS can be generated based on a cellidentifier for identifying a cell and the index of the synchronizationsignal block.

And, a part of bits included in a scrambling sequence of the PBCH maycorrespond to the index of the synchronization signal block.

Advantageous Effects

According to the present invention, since an index of a synchronizationsignal block is determined using a DMRS included in a resource region inwhich a PBCH is received, it is able to increase decoding performanceand reduce signaling overhead.

It will be appreciated by persons skilled in the art that that theeffects that could be achieved with the present invention are notlimited to what has been particularly described hereinabove and otheradvantages of the present invention will be more clearly understood fromthe following detailed description taken in conjunction with theaccompanying drawings.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram for structures of control and user planes of radiointerface protocol between a 3GPP radio access network standard-baseduser equipment and E-UTRAN;

FIG. 2 is a diagram for explaining physical channels used for 3GPPsystem and a general signal transmission method using the physicalchannels;

FIG. 3 is a diagram for a structure of a radio frame in LTE system;

FIG. 4 is a diagram illustrating a radio frame structure fortransmitting an SS (synchronization signal) in LTE system;

FIG. 5 illustrates a structure of a downlink radio frame in the LTEsystem;

FIG. 6 illustrates a structure of an uplink subframe in the LTE system;

FIG. 7 illustrates examples of a connection scheme between TXRUs andantenna elements.

FIG. 8 illustrates an example of a self-contained subframe structure;

FIG. 9 is a diagram for explaining an embodiment of mapping asynchronization signal sequence to a resource element;

FIG. 10 is a diagram for explaining an embodiment of generating aprimary synchronization signal sequence;

FIGS. 11 to 13 are diagrams for explaining a measurement result ofdetection performance of a transmitted synchronization signal and PAPR(peak to average power ratio) performance according to an embodiment ofthe present invention;

FIGS. 14 to 15 are diagrams for explaining embodiments of PSS/SSS/PBCHmultiplexed in a synchronization signal;

FIGS. 16 to 22 are diagrams for explaining a method of configuring asynchronization signal burst and a synchronization signal burst set;

FIGS. 23 to 29 are diagrams illustrating a method of indexing asynchronization signal and a method of indicating an index of thesynchronization signal, SFN, and a half frame;

FIGS. 30 to 56 are diagrams illustrating a performance measurementresult according to embodiments of the present invention;

FIGS. 57 to 59 are diagrams for explaining embodiments of configuring abandwidth for a synchronization signal and a downlink common channel;

FIG. 60 is a block diagram of a communication apparatus according to anembodiment of the present disclosure.

BEST MODE Mode for Invention

The configuration, operation, and other features of the presentdisclosure will readily be understood with embodiments of the presentdisclosure described with reference to the attached drawings.Embodiments of the present disclosure as set forth herein are examplesin which the technical features of the present disclosure are applied toa 3rd Generation Partnership Project (3GPP) system.

While embodiments of the present disclosure are described in the contextof Long Term Evolution (LTE) and LTE-Advanced (LTE-A) systems, they arepurely exemplary. Therefore, the embodiments of the present disclosureare applicable to any other communication system as long as the abovedefinitions are valid for the communication system.

The term ‘Base Station (BS)’ may be used to cover the meanings of termsincluding Remote Radio Head (RRH), evolved Node B (eNB or eNode B),Reception Point (RP), relay, etc.

FIG. 1 illustrates control-plane and user-plane protocol stacks in aradio interface protocol architecture conforming to a 3GPP wirelessaccess network standard between a User Equipment (UE) and an EvolvedUMTS Terrestrial Radio Access Network (E-UTRAN). The control plane is apath in which the UE and the E-UTRAN transmit control messages to managecalls, and the user plane is a path in which data generated from anapplication layer, for example, voice data or Internet packet data istransmitted.

A PHYsical (PHY) layer at Layer 1 (L1) provides information transferservice to its higher layer, a Medium Access Control (MAC) layer. ThePHY layer is connected to the MAC layer via transport channels. Thetransport channels deliver data between the MAC layer and the PHY layer.Data is transmitted on physical channels between the PHY layers of atransmitter and a receiver. The physical channels use time and frequencyas radio resources. Specifically, the physical channels are modulated inOrthogonal Frequency Division Multiple Access (OFDMA) for Downlink (DL)and in Single Carrier Frequency Division Multiple Access (SC-FDMA) forUplink (UL).

The MAC layer at Layer 2 (L2) provides service to its higher layer, aRadio Link Control (RLC) layer via logical channels. The RLC layer at L2supports reliable data transmission. RLC functionality may beimplemented in a function block of the MAC layer. A Packet DataConvergence Protocol (PDCP) layer at L2 performs header compression toreduce the amount of unnecessary control information and thusefficiently transmit Internet Protocol (IP) packets such as IP version 4(IPv4) or IP version 6 (IPv6) packets via an air interface having anarrow bandwidth.

A Radio Resource Control (RRC) layer at the lowest part of Layer 3 (orL3) is defined only on the control plane. The RRC layer controls logicalchannels, transport channels, and physical channels in relation toconfiguration, reconfiguration, and release of radio bearers. A radiobearer refers to a service provided at L2, for data transmission betweenthe UE and the E-UTRAN. For this purpose, the RRC layers of the UE andthe E-UTRAN exchange RRC messages with each other. If an RRC connectionis established between the UE and the E-UTRAN, the UE is in RRCConnected mode and otherwise, the UE is in RRC Idle mode. A Non-AccessStratum (NAS) layer above the RRC layer performs functions includingsession management and mobility management.

DL transport channels used to deliver data from the E-UTRAN to UEsinclude a Broadcast Channel (BCH) carrying system information, a PagingChannel (PCH) carrying a paging message, and a Shared Channel (SCH)carrying user traffic or a control message. DL multicast traffic orcontrol messages or DL broadcast traffic or control messages may betransmitted on a DL SCH or a separately defined DL Multicast Channel(MCH). UL transport channels used to deliver data from a UE to theE-UTRAN include a Random Access Channel (RACH) carrying an initialcontrol message and a UL SCH carrying user traffic or a control message.Logical channels that are defined above transport channels and mapped tothe transport channels include a Broadcast Control Channel (BCCH), aPaging Control Channel (PCCH), a Common Control Channel (CCCH), aMulticast Control Channel (MCCH), a Multicast Traffic Channel (MTCH),etc.

FIG. 2 illustrates physical channels and a general method fortransmitting signals on the physical channels in the 3GPP system.

Referring to FIG. 2, when a UE is powered on or enters a new cell, theUE performs initial cell search (S201). The initial cell search involvesacquisition of synchronization to an eNB. Specifically, the UEsynchronizes its timing to the eNB and acquires a cell Identifier (ID)and other information by receiving a Primary Synchronization Channel(P-SCH) and a Secondary Synchronization Channel (S-SCH) from the eNB.Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB. During the initial cellsearch, the UE may monitor a DL channel state by receiving a DownLinkReference Signal (DL RS).

After the initial cell search, the UE may acquire detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation included in the PDCCH (S202).

If the UE initially accesses the eNB or has no radio resources forsignal transmission to the eNB, the UE may perform a random accessprocedure with the eNB (S203 to S206). In the random access procedure,the UE may transmit a predetermined sequence as a preamble on a PhysicalRandom Access Channel (PRACH) (S203 and S205) and may receive a responsemessage to the preamble on a PDCCH and a PDSCH associated with the PDCCH(S204 and S206). In the case of a contention-based RACH, the UE mayadditionally perform a contention resolution procedure.

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S207) and transmit a Physical Uplink Shared Channel(PUSCH) and/or a Physical Uplink Control Channel (PUCCH) to the eNB(S208), which is a general DL and UL signal transmission procedure.Particularly, the UE receives Downlink Control Information (DCI) on aPDCCH. Herein, the DCI includes control information such as resourceallocation information for the UE. Different DCI formats are definedaccording to different usages of DCI.

Control information that the UE transmits to the eNB on the UL orreceives from the eNB on the DL includes a DL/UL ACKnowledgment/NegativeACKnowledgment (ACK/NACK) signal, a Channel Quality Indicator (CQI), aPrecoding Matrix Index (PMI), a Rank Indicator (RI), etc. In the 3GPPLTE system, the UE may transmit control information such as a CQI, aPMI, an RI, etc. on a PUSCH and/or a PUCCH.

FIG. 3 illustrates a structure of a radio frame used in the LTE system.

Referring to FIG. 3, a radio frame is 10 ms (327200×Ts) long and dividedinto 10 equal-sized subframes. Each subframe is 1 ms long and furtherdivided into two slots. Each time slot is 0.5 ms (15360×Ts) long.Herein, Ts represents a sampling time and Ts=1/(15 kHz×2048)=3.2552×10−8(about 33 ns). A slot includes a plurality of Orthogonal FrequencyDivision Multiplexing (OFDM) symbols or SC-FDMA symbols in the timedomain by a plurality of Resource Blocks (RBs) in the frequency domain.In the LTE system, one RB includes 12 subcarriers by 7 (or 6) OFDMsymbols. A unit time during which data is transmitted is defined as aTransmission Time Interval (TTI). The TTI may be defined in units of oneor more subframes. The above-described radio frame structure is purelyexemplary and thus the number of subframes in a radio frame, the numberof slots in a subframe, or the number of OFDM symbols in a slot mayvary.

FIG. 4 is a diagram illustrating a radio frame structure fortransmitting an SS (synchronization signal) in LTE system. Inparticular, FIG. 4 illustrates a radio frame structure for transmittinga synchronization signal and PBCH in FDD (frequency division duplex).FIG. 4 (a) shows positions at which the SS and the PBCH are transmittedin a radio frame configured by a normal CP (cyclic prefix) and FIG. 4(b) shows positions at which the SS and the PBCH are transmitted in aradio frame configured by an extended CP.

An SS will be described in more detail with reference to FIG. 4. An SSis categorized into a PSS (primary synchronization signal) and an SSS(secondary synchronization signal). The PSS is used to acquiretime-domain synchronization such as OFDM symbol synchronization, slotsynchronization, etc. and/or frequency-domain synchronization. And, theSSS is used to acquire frame synchronization, a cell group ID, and/or aCP configuration of a cell (i.e. information indicating whether to anormal CP or an extended is used). Referring to FIG. 4, a PSS and an SSSare transmitted through two OFDM symbols in each radio frame.Particularly, the SS is transmitted in first slot in each of subframe 0and subframe 5 in consideration of a GSM (Global System for Mobilecommunication) frame length of 4.6 ms for facilitation of inter-radioaccess technology (inter-RAT) measurement. Especially, the PSS istransmitted in a last OFDM symbol in each of the first slot of subframe0 and the first slot of subframe 5. And, the SSS is transmitted in asecond to last OFDM symbol in each of the first slot of subframe 0 andthe first slot of subframe 5. Boundaries of a corresponding radio framemay be detected through the SSS. The PSS is transmitted in the last OFDMsymbol of the corresponding slot and the SSS is transmitted in the OFDMsymbol immediately before the OFDM symbol in which the PSS istransmitted. According to a transmission diversity scheme for the SS,only a single antenna port is used. However, the transmission diversityscheme for the SS standards is not separately defined in the currentstandard.

Referring to FIG. 4, by detecting the PSS, a UE may know that acorresponding subframe is one of subframe 0 and subframe 5 since the PSSis transmitted every 5 ms but the UE cannot know whether the subframe issubframe 0 or subframe 5. That is, frame synchronization cannot beobtained only from the PSS. The UE detects the boundaries of the radioframe in a manner of detecting an SSS which is transmitted twice in oneradio frame with different sequences.

Having demodulated a DL signal by performing a cell search procedureusing the PSS/SSS and determined time and frequency parameters necessaryto perform UL signal transmission at an accurate time, a UE cancommunicate with an eNB only after obtaining system informationnecessary for a system configuration of the UE from the eNB.

The system information is configured with a master information block(MIB) and system information blocks (SIBs). Each SIB includes a set offunctionally related parameters and is categorized into an MIB, SIB Type1 (SIB1), SIB Type 2 (SIB2), and SIB3 to SIB8 according to the includedparameters.

The MIB includes most frequently transmitted parameters which areessential for a UE to initially access a network served by an eNB. TheUE may receive the MIB through a broadcast channel (e.g. a PBCH). TheMIB includes a downlink system bandwidth (DL BW), a PHICH configuration,and a system frame number (SFN). Thus, the UE can explicitly knowinformation on the DL BW, SFN, and PHICH configuration by receiving thePBCH. On the other hand, the UE may implicitly know information on thenumber of transmission antenna ports of the eNB. The information on thenumber of the transmission antennas of the eNB is implicitly signaled bymasking (e.g. XOR operation) a sequence corresponding to the number ofthe transmission antennas to 16-bit CRC (cyclic redundancy check) usedin detecting an error of the PBCH.

The SIB1 includes not only information on time-domain scheduling forother SIBs but also parameters necessary to determine whether a specificcell is suitable in cell selection. The UE receives the SIB1 viabroadcast signaling or dedicated signaling.

A DL carrier frequency and a corresponding system bandwidth can beobtained by MIB carried by PBCH. A UL carrier frequency and acorresponding system bandwidth can be obtained through systeminformation corresponding to a DL signal. Having received the MIB, ifthere is no valid system information stored in a corresponding cell, aUE applies a value of a DL BW included in the MIB to a UL bandwidthuntil system information block type 2 (SystemInformationBlockType2,SIB2) is received. For example, if the UE obtains the SIB2, the UE isable to identify the entire UL system bandwidth capable of being usedfor UL transmission through UL-carrier frequency and UL-bandwidthinformation included in the SIB2.

In the frequency domain, PSS/SSS and PBCH are transmitted irrespectiveof an actual system bandwidth in total 6 RBs, i.e., 3 RBs in the leftside and 3 RBs in the right side with reference to a DC subcarrierwithin a corresponding OFDM symbol. In other words, the PSS/SSS and thePBCH are transmitted only in 72 subcarriers. Therefore, a UE isconfigured to detect or decode the SS and the PBCH irrespective of adownlink transmission bandwidth configured for the UE.

Having completed the initial cell search, the UE can perform a randomaccess procedure to complete the accessing the eNB. To this end, the UEtransmits a preamble via PRACH (physical random access channel) and canreceive a response message via PDCCH and PDSCH in response to thepreamble. In case of contention based random access, it may transmitadditional PRACH and perform a contention resolution procedure such asPDCCH and PDSCH corresponding to the PDCCH.

Having performed the abovementioned procedure, the UE can performPDCCH/PDSCH reception and PUSCH/PUCCH transmission as a general UL/DLsignal transmission procedure.

The random access procedure is also referred to as a random accesschannel (RACH) procedure. The random access procedure is used forvarious usages including initial access, UL synchronization adjustment,resource allocation, handover, and the like. The random access procedureis categorized into a contention-based procedure and a dedicated (i.e.,non-contention-based) procedure. In general, the contention-based randomaccess procedure is used for performing initial access. On the otherhand, the dedicated random access procedure is restrictively used forperforming handover, and the like. When the contention-based randomaccess procedure is performed, a UE randomly selects a RACH preamblesequence. Hence, a plurality of UEs can transmit the same RACH preamblesequence at the same time. As a result, a contention resolutionprocedure is required thereafter. On the contrary, when the dedicatedrandom access procedure is performed, the UE uses an RACH preamblesequence dedicatedly allocated to the UE by an eNB. Hence, the UE canperform the random access procedure without a collision with a differentUE.

The contention-based random access procedure includes 4 steps describedin the following. Messages transmitted via the 4 steps can berespectively referred to as message (Msg) 1 to 4 in the presentinvention.

-   -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response (RAR) (via PDCCH and PDSCH (eNB        to)    -   Step 3: Layer 2/Layer 3 message (via PUSCH) (UE to eNB)    -   Step 4: Contention resolution message (eNB to UE)

On the other hand, the dedicated random access procedure includes 3steps described in the following. Messages transmitted via the 3 stepscan be respectively referred to as message (Msg) 0 to 2 in the presentinvention. It may also perform uplink transmission (i.e., step 3)corresponding to PAR as a part of the ransom access procedure. Thededicated random access procedure can be triggered using PDCCH(hereinafter, PDCCH order) which is used for an eNB to indicatetransmission of an RACH preamble.

-   -   Step 0: RACH preamble assignment via dedicated signaling (eNB to        UE)    -   Step 1: RACH preamble (via PRACH) (UE to eNB)    -   Step 2: Random access response(RAR) (via PDCCH and PDSCH) (eNB        to UE)

After the RACH preamble is transmitted, the UE attempts to receive arandom access response (RAR) in a preconfigured time window.Specifically, the UE attempts to detect PDCCH (hereinafter, RA-RNTIPDCCH) (e.g., a CRC masked with RA-RNTI in PDCCH) having RA-RNTI (randomaccess RNTI) in a time window. If the RA-RNTI PDCCH is detected, the UEchecks whether or not there is a RAR for the UE in PDSCH correspondingto the RA-RNTI PDCCH. The RAR includes timing advance (TA) informationindicating timing offset information for UL synchronization, UL resourceallocation information (UL grant information), a temporary UE identifier(e.g., temporary cell-RNTI, TC-RNTI), and the like. The UE can performUL transmission (e.g., message 3) according to the resource allocationinformation and the TA value included in the RAR. HARQ is applied to ULtransmission corresponding to the RAR. In particular, the UE can receivereception response information (e.g., PHICH) corresponding to themessage 3 after the message 3 is transmitted.

A random access preamble (i.e. RACH preamble) consists of a cyclicprefix of a length of TCP and a sequence part of a length of TSEQ. TheTCP and the TSEQ depend on a frame structure and a random accessconfiguration. A preamble format is controlled by higher layer. The RACHpreamble is transmitted in a UL subframe. Transmission of the randomaccess preamble is restricted to a specific time resource and afrequency resource. The resources are referred to as PRACH resources. Inorder to match an index 0 with a PRB and a subframe of a lower number ina radio frame, the PRACH resources are numbered in an ascending order ofPRBs in subframe numbers in the radio frame and frequency domain. Randomaccess resources are defined according to a PRACH configuration index(refer to 3GPP TS 36.211 standard document). The RACH configurationindex is provided by a higher layer signal (transmitted by an eNB).

In LTE/LTE-A system, subcarrier spacing for a random access preamble(i.e., RACH preamble) is regulated by 1.25 kHz and 7.5 kHz for preambleformats 0 to 3 and a preamble format 4, respectively (refer to 3GPP TS36.211).

FIG. 5 illustrates exemplary control channels included in a controlregion of a subframe in a DL radio frame.

Referring to FIG. 5, a subframe includes 14 OFDM symbols. The first oneto three OFDM symbols of a subframe are used for a control region andthe other 13 to 11 OFDM symbols are used for a data region according toa subframe configuration. In FIG. 5, reference characters R1 to R4denote RSs or pilot signals for antenna 0 to antenna 3. RSs areallocated in a predetermined pattern in a subframe irrespective of thecontrol region and the data region. A control channel is allocated tonon-RS resources in the control region and a traffic channel is alsoallocated to non-RS resources in the data region. Control channelsallocated to the control region include a Physical Control FormatIndicator Channel (PCFICH), a Physical Hybrid-ARQ Indicator Channel(PHICH), a Physical Downlink Control Channel (PDCCH), etc.

The PCFICH is a physical control format indicator channel carryinginformation about the number of OFDM symbols used for PDCCHs in eachsubframe. The PCFICH is located in the first OFDM symbol of a subframeand configured with priority over the PHICH and the PDCCH. The PCFICHincludes 4 Resource Element Groups (REGs), each REG being distributed tothe control region based on a cell Identity (ID). One REG includes 4Resource Elements (REs). An RE is a minimum physical resource defined byone subcarrier by one OFDM symbol. The PCFICH is set to 1 to 3 or 2 to 4according to a bandwidth. The PCFICH is modulated in Quadrature PhaseShift Keying (QPSK).

The PHICH is a physical Hybrid-Automatic Repeat and request (HARQ)indicator channel carrying an HARQ ACK/NACK for a UL transmission. Thatis, the PHICH is a channel that delivers DL ACK/NACK information for ULHARQ. The PHICH includes one REG and is scrambled cell-specifically. AnACK/NACK is indicated in one bit and modulated in Binary Phase ShiftKeying (BPSK). The modulated ACK/NACK is spread with a Spreading Factor(SF) of 2 or 4. A plurality of PHICHs mapped to the same resources forma PHICH group. The number of PHICHs multiplexed into a PHICH group isdetermined according to the number of spreading codes. A PHICH (group)is repeated three times to obtain a diversity gain in the frequencydomain and/or the time domain.

The PDCCH is a physical DL control channel allocated to the first n OFDMsymbols of a subframe. Herein, n is 1 or a larger integer indicated bythe PCFICH. The PDCCH occupies one or more CCEs. The PDCCH carriesresource allocation information about transport channels, PCH andDL-SCH, a UL scheduling grant, and HARQ information to each UE or UEgroup. The PCH and the DL-SCH are transmitted on a PDSCH. Therefore, aneNB and a UE transmit and receive data usually on the PDSCH, except forspecific control information or specific service data.

Information indicating one or more UEs to receive PDSCH data andinformation indicating how the UEs are supposed to receive and decodethe PDSCH data are delivered on a PDCCH. For example, on the assumptionthat the Cyclic Redundancy Check (CRC) of a specific PDCCH is masked byRadio Network Temporary Identity (RNTI) “A” and information about datatransmitted in radio resources (e.g. at a frequency position) “B” basedon transport format information (e.g. a transport block size, amodulation scheme, coding information, etc.) “C” is transmitted in aspecific subframe, a UE within a cell monitors, that is, blind-decodes aPDCCH using its RNTI information in a search space. If one or more UEshave RNTI “A”, these UEs receive the PDCCH and receive a PDSCH indicatedby “B” and “C” based on information of the received PDCCH.

FIG. 6 illustrates a structure of a UL subframe in the LTE system.

Referring to FIG. 6, a UL subframe may be divided into a control regionand a data region. A Physical Uplink Control Channel (PUCCH) includingUplink Control Information (UCI) is allocated to the control region anda Physical uplink Shared Channel (PUSCH) including user data isallocated to the data region. The middle of the subframe is allocated tothe PUSCH, while both sides of the data region in the frequency domainare allocated to the PUCCH. Control information transmitted on the PUCCHmay include an HARQ ACK/NACK, a CQI representing a downlink channelstate, an RI for Multiple Input Multiple Output (MIMO), a SchedulingRequest (SR) requesting UL resource allocation. A PUCCH for one UEoccupies one RB in each slot of a subframe. That is, the two RBsallocated to the PUCCH are frequency-hopped over the slot boundary ofthe subframe. Particularly, PUCCHs with m=0, m=1, and m=2 are allocatedto a subframe in FIG. 6.

Hereinafter, channel state information (CSI) reporting will be describedbelow. In the current LTE standard, there are two MIMO transmissionschemes, open-loop MIMO operating without channel information andclosed-loop MIMO operating with channel information. Particularly in theclosed-loop MIMO, each of an eNB and a UE may perform beamforming basedon CSI to obtain the multiplexing gain of MIMO antennas. To acquire CSIfrom the UE, the eNB may command the UE to feed back CSI on a downlinksignal by allocating a PUCCH(Physical Uplink Control CHannel) or aPUSCH(Physical Uplink Shared CHannel) to the UE.

The CSI is largely classified into three information types, RI (RankIndicator), PMI (Precoding Matrix), and CQI (Channel QualityIndication). First of all, the RI indicates rank information of achannel as described above, and means the number of streams that may bereceived by a UE through the same time-frequency resources. Also, sincethe RI is determined by long-term fading of a channel, the RI may be fedback to an eNB in a longer period than a PMI value and a CQI value.

Second, the PMI is a value obtained by reflecting spatialcharacteristics of a channel, and indicates a precoding matrix index ofan eNB, which is preferred by the UE based on a metric such as signal tointerference and noise ratio (SINR). Finally, the CQI is a valueindicating channel strength, and generally means a reception SINR thatmay be obtained by the eNB when the PMI is used.

In the 3GPP LTE-A system, the eNB may configure a plurality of CSIprocesses for the UE, and may be reported CSI for each of the CSIprocesses. In this case, the CSI process includes CSI-RS resource forspecifying signal quality and CSI-IM (interference measurement)resource, that is, IMR (interference measurement resource) forinterference measurement.

Since a wavelength becomes short in the field of Millimeter Wave (mmW),a plurality of antenna elements may be installed in the same area. Inmore detail, a wavelength is 1 cm in a band of 30 GHz, and a total of64(8×8) antenna elements of a 2D array may be installed in a panel of 4by 4 cm at an interval of 0.5 lambda(wavelength). Therefore, a recenttrend in the field of mmW attempts to increase coverage or throughput byenhancing BF (beamforming) gain using a plurality of antenna elements.

In this case, if a transceiver unit (TXRU) is provided to control atransmission power and phase per antenna element, independentbeamforming may be performed for each frequency resource. However, aproblem occurs in that effectiveness is deteriorated in view of costwhen TXRU is provided for all of 100 antenna elements. Therefore, ascheme is considered, in which a plurality of antenna elements aremapped into one TXRU and a beam direction is controlled by an analogphase shifter. Since this analog beamforming scheme may make only onebeam direction in a full band, a problem occurs in that frequencyselective beamforming is not available.

As an intermediate type of digital BF and analog BF, a hybrid BF havingB TXRUs smaller than Q antenna elements may be considered. In this case,although there is a difference depending on a connection scheme of BTXRUs and Q antenna elements, the number of beam directions that enablesimultaneous transmission is limited to B or less.

FIG. 7 illustrates examples of a connection scheme between TXRUs andantenna elements.

(a) of FIG. 7 illustrates that TXRU is connected to a sub-array. In thiscase, the antenna elements are connected to only one TXRU. Unlike (a) ofFIG. 7, (b) of FIG. 7 illustrates that TXRU is connected to all antennaelements. In this case, the antenna elements are connected to all TXRUs.In FIG. 7, W indicates a phase vector multiplied by an analog phaseshifter. That is, a direction of analog beamforming is determined by W.In this case, mapping between CSI-RS antenna ports and TXRUs may be1-to-1 or 1-to-many.

As more communication devices require greater communication capacity,the need of mobile broadband communication more advanced than theconventional RAT (radio access technology) has been issued. Also,massive MTC (Machine Type Communications) technology that providesvarious services anywhere and at any time by connecting a plurality ofdevices and things is one of main issues which will be considered innext generation communication. Furthermore, a communication systemdesign considering service/UE susceptible to reliability and latency hasbeen discussed. Considering this status, the introduction of the nextgeneration RAT has been discussed, and the next generation RAT will bereferred to as NewRAT in the present invention.

A self-contained subframe structure shown in FIG. 8 is considered in thefifth generation NewRAT to minimize data transmission latency in a TDDsystem. FIG. 8 illustrates an example of a self-contained subframestructure.

In FIG. 8, oblique line areas indicate downlink control regions andblack colored areas indicate uplink control regions. Areas having nomark may be used for downlink data transmission or uplink datatransmission. In this structure, downlink transmission and uplinktransmission are performed in due order within one subframe, wherebydownlink data may be transmitted and uplink ACK/NACK may be receivedwithin the subframe. As a result, the time required for datare-transmission may be reduced when an error occurs in datatransmission, whereby latency of final data transfer may be minimized.

In this self-contained subframe structure, a time gap for switching froma transmission mode to a reception mode or vice versa is required forthe base station and the UE. To this end, some OFDM symbols (OS) at thetime when a downlink is switched to an uplink in the self-containedsubframe structure are set to a guard period.

Examples of the self-contained subframe type that may be configured inthe system operating based on the NewRAT may consider four subframetypes as follows.

-   -   downlink control period+downlink data period+GP+uplink control        period    -   downlink control period+downlink data period    -   downlink control period+GP+uplink data period+uplink control        period    -   downlink control period+GP+uplink data period

In the following, a method of generating a synchronization signal and amethod of indicating a synchronization signal index are describedaccording to embodiments of the present invention.

1. Parameter Set and Basic Subcarrier Spacing

A parameter set for an SS block can be defined according to thefollowing.

-   -   Subcarrier spacing (bandwidth)

15 kHz (up to 5 MHz), 30 kHz (up to 10 MHz), 120 kHz (up to 40 MHz), 240kHz (up to 80 MHz)

Since 24 RBs are allocated to transmit PBCH, it is necessary to have atransmission bandwidth of 4.32 MHz for a subcarrier of 15 kHz and atransmission bandwidth of 34.56 MHz for a subcarrier of 120 kHz. And, ina frequency range up to 6 GHz, a minimum available carrier bandwidth forNR is determined by 5 MHz. In a frequency range ranging from 6 GHz to52.6 GHz, a minimum available carrier bandwidth for NR is determined by50 MHz.

In particular, as mentioned in the foregoing description, in a frequencyrange narrower than 6 GHz, subcarrier spacing of 15 kHz is determined asdefault numerology. In a frequency range wider than 6 GHz, subcarrierspacing of 120 kHz can be determined as default numerology. Morespecifically, in a frequency range ranging from 6 GHz to 52.6 GHz,subcarrier spacing of 120 kHz can be determined as default numerology.However, it is necessary to delicately approach detection performance ofPSS/SSS-based 15 kHz subcarrier in 6 GHz.

And, it may consider the possibility of introducing wider subcarrierspacing (e.g., 30 kHz or 240 kHz subcarrier spacing) for transmitting anNR-SS.

2. Transmission Bandwidth and NR-SS Sequence RE Mapping

Referring to FIG. 9, similar to a mapping method of a PSS/SSS sequencemapped to an RE in LTE, an NR-SS sequence can be mapped to REspositioned at the center of a transmission bandwidth. A partial REpositioned at an edge of the transmission bandwidth can be reserved as aguard subcarrier. For example, when 12 RBs are used for transmitting anNR-SS, 127 REs are used for an NR-SS sequence and 17 REs are reserved.In this case, a 64^(th) element of the NR-SS sequence can be mapped to asubcarrier positioned at the center of the bandwidth on which the NR-SSis transmitted.

Meanwhile, when an NR-SS sequence is mapped to an RE, in case of 15 kHzsubcarrier, it may assume that a transmission bandwidth of 2.16 MHz isused for transmitting an NR-SS. If subcarrier spacing increases by aninteger multiple, an NR-SS bandwidth identically increases by an integermultiple as well.

In particular, a bandwidth for transmitting an NR-SS can be defined asfollows according to subcarrier spacing.

-   -   If subcarrier spacing corresponds to 15 kHz, the bandwidth for        transmitting the NR-SS may correspond to 2.16 MHz.    -   If subcarrier spacing corresponds to 30 kHz, the bandwidth for        transmitting the NR-SS may correspond to 4.32 MHz.    -   If subcarrier spacing corresponds to 120 kHz, the bandwidth for        transmitting the NR-SS may correspond to 17.28 MHz.    -   If subcarrier spacing corresponds to 240 kHz, the bandwidth for        transmitting the NR-SS may correspond to 34.56 MHz.

3. NR-PSS Sequence Design

In NR system, in order to classify 1000 cell IDs, the number of NR-PSSsequences is defined by 3 and the number of hypothesis of NR-SSScorresponding to each NR-PSS is defined by 344.

When NR-PSS is designed, it is necessary consider timing ambiguity,PAPR, detection complexity, and the like. In order to solve the timingambiguity, it may be able to generate an NR-PSS sequence using anM-sequence of frequency domain. However, if the NR-PSS sequence isgenerated using the M-sequence, it may have relatively high PAPRcharacteristic. Hence, when the NR-PSS is designed, it is necessary tostudy on a frequency domain M-sequence with a low PAPR characteristic.

Meanwhile, it may consider a modified ZC sequence as an NR-PSS sequence.In particular, if 4 ZC sequences are generated in a manner of beingconsecutively arranged in time domain, it may be able to solve a timingambiguity problem, have a low PAPR characteristic, and reduce detectioncomplexity. In particular, in NR system, when a UE intends to detect anNR-PSS having a transmission bandwidth wider than that of multi-sequenceand LTE, detection complexity increases. Hence, it is very important toreduce the detection complexity in designing the NR-PSS.

Based on the aforementioned discussion, it may consider two types ofNR-PSS sequence.

(1) Frequency M-sequence with low PAPR characteristic

-   -   Polynomial expression: g(x)=x⁷+x⁶+x⁴+x+1 (initial poly shift        register value: 1000000)    -   Cyclic shift: 0, 31, 78

(2) 4 ZC Sequences Consecutively Arranged in Time Domain

-   -   ZC sequence of a length of 31 (root index: {1,30}, {7,24},        {4,27})    -   Equation for generating a sequence

$\begin{matrix}{{{{d(i)} = {{DFT}( \lbrack {s\; 1_{u_{1}}s\; 2_{u_{2}}s\; 3_{u_{1}}s\; 4_{u_{2}}} \rbrack )}},{i = {0 \sim 127}}}{{where},{{s\; 1_{u_{1}}(n)} = \{ {{{\begin{matrix}{e^{{- j}\frac{\pi \; {u_{1}{({n + 1})}}}{31}},} & {{n = 0},1,\ldots \mspace{14mu},30} \\{0,} & {n = 31}\end{matrix}s\; 2_{u_{2}}(n)} = {s\; 1_{u_{2}}(n)}},{n = 0},1,\ldots \mspace{14mu},{{31s\; 3_{u_{1}}(n)} = {s\; 1_{u_{1}}(n)}},{n = 0},1,\ldots \mspace{14mu},{{31s\; 4_{u_{2}}(n)} = {s\; 1_{u_{2}}(n)}},{n = 0},1,\ldots \mspace{14mu},31} }}} & \lbrack {{Equation}\mspace{14mu} 1} \rbrack\end{matrix}$

FIG. 10 is a diagram for briefly explaining a method of generating anNR-PSS using 4 consecutive ZC sequences in time domain. Referring toFIG. 10, when the N number of sub-symbols correspond to S1, S2, . . . ,Sn, if sequences of the sub-symbols are concatenated before IFFT isperformed, DFT (Discrete Fourier Transform) spreading is performed witha length of the total sequences, a plurality of sequences respectivelycorresponding to the N number of sub-symbols are mapped according to asubcarrier, and IFFT is performed, it may be able to obtain a timedomain sequence of a length of NIFFT without a problem of out of bandemission.

4. NR-SSS Sequence Design

An NR-SSS sequence is generated by a single long sequence and isgenerated by a combination of 2 M-sequences having a differentpolynomial expression to generate 334 hypotheses. For example, if acyclic shift value for a first M-sequence corresponds to 112 and acyclic shift value for a second M-sequence corresponds 3, it may obtain336 hypotheses in total. In this case, it may be able to obtain ascrambling sequence for an NR-PSS by applying a third M-sequence.

If an NR-SS burst set of a relatively short period (e.g., 5 ms/10 ms) isconfigured, the NR-SS burst set can be transmitted several times in tworadio frames each of which has a length of 10 ms.

In particular, if a different NR-SSS sequence is introduced for theNR-SS burst set which is transmitted several times, in other word, if adifferent NR-SSS sequence is used whenever the NR-SS burst set istransmitted, a UE is able to identify each of a plurality of NR-SS burstsets transmitted within a basic period.

For example, if NR-SS bust sets are transmitted 4 times in a basicperiod, it may consider that an original set of an NR-SSS sequence isapplied to a first NR-SSS burst set and an NR-SSS sequence differentfrom the original set is applied to a second, a third, and a fourthNR-SS burst set. If two NR-SSS sequence sets different from each otherare used, an NR-SSS sequence set is used for the first and the thirdNR-SSS burst set and another NR-SSS sequence set can be used for thesecond and the fourth NR-SSS burst set.

In NR system, two M-sequences each of which has a length of 127 aredefined for an NR-SSS sequence and a final sequence is generated bymultiplying elements included in each of the M-sequences.

In particular, the NR-SSS sequence may correspond to a scramblingsequence given by an NR-SSS, the NR-SSS sequence may have a length of127, and the NR-SSS sequence can be determined by an equation 2described in the following.

d(n)=s _(1,m)(n)s _(2,k)(n)c _(z)(n) for n=0, . . . ,126 andz=0,1  [Equation 2]

In this case, z=0 can be used for an NR-SSS transmitted in a first SSburst set of two radio frames each of which has a length of 10 ms. And,z=1 can be used for an NR-SSS transmitted in a second, a third, and afourth SS burst set.

In this case, s_(1,m)(n) and s_(2,k)(n) can be determined by an equation3 described in the following.

s _(1,m)(n)=S ₁((n+m)mod 127),

s _(2,k)(n)=S ₂((n+k)mod 127)  [Equation 3]

In this case, it may define m=N_(ID1) mod 112, K=floor(N_(ID1)/112),k=CS₂(K), 0≤N_(ID1)≤333, CS₂∈{48, 67,122}.

Lastly, in order to calculate S1 and S2, S_(r)(i)=1−2x(i), 0≤i≤126,r=1,2 can be defined. In this case, a polynomial expression for x(i) canbe defined by an equation 4 described in the following.

x(j+7)=(x(j+3)+x(j))mod 2,r=1

x(j+7)=(x(j+3)+x(j+2)+x(j+1)+x(j))mod 2,r=2  [Equation 4]

In this case, an initial condition for the x(i) may correspond to

x(0)=x(1)=x(2)=x(3)=x(4)=x(5)=0, x(6)=1 and may have a value satisfying0≤j≤119.

In this case, as a preamble and a mid-amble of an SSS, it may be able touse two scrambling sequences including C₀(n) and C₁(n). The twoscrambling sequences depend on a PSS. As shown in an equation 5 in thefollowing, the scrambling sequences can be defined by applying adifferent cyclic shift to C(n) corresponding to an M-sequence.

c _(z)(n)=C((n+p)mod 127)  [Equation 5]

where, p=CS₁(N_(ID2)+3·z), CS₁{23, 69, 103, 64, 124, 24}, N_(ID2)∈{0,1,2}

In this case, C(i)=1−2x(i) and 0≤I≤126 can be defined. In this case, apolynomial expression for the x(i) can be defined by an equation 6described in the following.

x(j+7)=(x(j+5)+x(j+4)+x(j+3)+x(j+2)+x(j+1)+x(j))mod 2  [Equation 6]

In this case, an initial condition for the x(i) may correspond tox(0)=x(1)=x(2)=x(3)=x(4)=x(5)=0, x(6)=1 and may have a value satisfying0≤j≤119.

In the following, performance measurement results according to theaforementioned embodiments are described. In order to measureperformance of an NR-PSS, 3 methods of designing the NR-SSS areconsidered: 1) frequency domain M-sequence (legacy PSS sequence), 2)M-sequence with low PAPR, and 3) sequence generated by concatenating 4ZC sequences in time domain.

And, in order to measure an NR-SSS, an NR-SSS sequence proposed by thepresent invention is used.

5. Measurement Result According to the Aforementioned NR-PSS SequenceDesign

PAPR and CM

Measurement results of PAPR and CM measured for the 3 types of NR-PSSsequence are shown in Table 1 in the following.

TABLE 1 PAPR [dB] CM [dB] Frequency domain M-sequence (WA) 4.87, 5.10,5.74 1.25, 1.76, 2.19 M-sequence with low PAPR 4.16, 3.99, 4.15 1.10,1.42, 1.50 Four ZC sequences concatenation 2.80, 3.49, 3.91 0.094, 0.71,0.79 in time

According to the results, PAPR/CM of an NR-SSS based on a sequence ofwhich 4 ZC sequences are concatenated in time domain is lower thanPAPR/CM of an NR-PSS based on an M-sequence. Meanwhile, when anM-sequence with low PAPR is compared with a frequency domain M-sequence,PAPR/CM of the M-sequence with low PAPR is lower than PAPR/CM of thefrequency domain M-sequence. Meanwhile, since the PAPR/CM corresponds toan important element for determining a price of a power amplifier, it isnecessary to consider designing an NR-PSS of which the PAPR/CM is low.

Consequently, in the aspect of the PAPR/CM, an NR-PSS based on a ZCsequence shows a better performance measurement result compared to anNR-PSS based on an M-sequence. An NR-PSS based on an M-sequence with lowPAPR shows a better performance measurement result compared to an NR-PSSof a frequency domain M-sequence.

Misdetection Rate

FIG. 11 illustrates evaluation for a misdetection rate of each of theaforementioned NR-PSSs. Referring to FIG. 11, it is able to know thatperformance of each of NR-PSS designs has a similar level. On the otherhand, referring to FIG. 12, it is able to see that a sequence generatedby concatenating 4 ZC sequences has a lowest detection complexity.

Specifically, referring to FIG. 12, it is able to see that a sequencegenerated by concatenating 4 ZC sequences and a frequency domainsequence have similar detection performance. In this case, the sequencegenerated by concatenating 4 ZC sequences has a merit in that detectioncomplexity is lower. If it is assumed that the NR-PSS sequence hassimilar detection complexity, the sequence generated by concatenating 4ZC sequences provides superior performance compared to the M-sequence.

Consequently, NR-PSS design detection performance based on a ZC sequenceprovides better performance compared to detection performance of thefrequency domain M-sequence under the assumption of the same detectioncomplexity.

6. Measurement Result According to the Aforementioned NR-SSS SequenceDesign

In the following, detection performances are compared with each otheraccording to the number of NR-SSS sequences. In order to measureperformance, a legacy SSS sequence is compared with an NR-SSS proposedin the present invention.

Information on NR-SSS sequence design is briefly explained in thefollowing.

1) NR-SSS of a single set (334 hypotheses per NR-PSS sequence)

2) NR-SSS of two sets (668 hypotheses per NR-PSS sequence)

Referring to FIG. 13, although the hypotheses of NR-SSS are doubled, nospecial performance degrade is examined. Hence, in order to detect aboundary of an SS bust set within a basic period, it may considerintroducing an additional set of an NR-SSS.

Meanwhile, parameters used for a measurement experiment according toFIGS. 11 to 13 are shown in Table 2 in the following.

TABLE 2 Parameter Value Carrier Frequency 4 GHz Channel Model CDL_C(delay scaling values: 100 ns) Subcarrier Spacing 15 kHz AntennaConfiguration TRP: (1, 1, 2) with Omni-directional antenna element UE:(1, 1, 2) with Omni-directional antenna element Timing offset Uniformlydistributed in [−1 ms, 1 ms] Frequency Offset 5 ppm PSS/SSS detectionOne shot detection PSS/SSS period 20 ms Subframe duration  1 ms OFDMsymbols in SF 14 Number of interfering TRPs 2 Operating SNR −6 dB

7. SS Block Configuration

When the maximum payload size of PBCH corresponds to 80 bits, it may beable to use 4 OFDM symbols in total to transmit an SS block. Meanwhile,it is necessary to consider a time position of NR-PSS/NR-SSS/NR-PBCH inan SS block including the NR-PSS, the NR-SSS, and the NR-PBCH. Wheninitial access is performed, the NR-PBCH can be used as a referencesignal for precise time/frequency tracking. In order to increaseestimation accuracy, two OFDM symbols for the NR-PBCH can be positionedat a distance as far as possible. In particular, as shown in FIG. 14(a), the present invention proposes to use a first and a fourth OFDMsymbol of an SS block to transmit the NR-PBCH. Hence, a second OFDMsymbol is allocated to the NR-SSS and a third OFDM symbol can be usedfor the NR-SSS.

Meanwhile, when the NR-SSS is transmitted to measure or discover a cell,it is not necessary to transmit both the NR-PBCH and an SS block timeindex indication. In this case, as shown in FIG. 14 (b), an SS blockincludes two OFDM symbols. A first OFDM symbol is allocated to theNR-SSS and a second OFDM symbol is allocated to the NR-SSS.

When a PBCH decoding performance is measured in accordance with thenumber of REs for a DMRS, if two OFDM symbols are allocated, 192 REs areused for the DMRS and 384 REs can be used for data. In this case, if aPBCH payload size corresponds to 64 bits, it may be able to obtain 1/12coding speed corresponding to the coding speed of LTE PBCH.

It may consider a method of mapping a coded NR-PBCH bit via an RE in aPBCH symbol. However, the method has a demerit in the aspect ofinterference and decoding performance. On the contrary, if a codedNR-PBCH bit is mapped over REs included in the N number of PBCH symbols,it may have better performance in the aspect of interference anddecoding performance.

Meanwhile, when bits are coded over two OFDM symbols using the samemethod and bits are coded over two OFDM symbols using a differentmethod, since the bits, which are coded over the two OFDM symbols usingthe different method, have more redundant bits, the latter methodprovides better performance. Hence, it may consider using the bits whichare coded over the two OFDM symbols using the different method.

NR system supports various numerologies. Hence, numerology fortransmitting an SS block may be different from numerology fortransmitting data. And, if channels (e.g., PBCH and PDSCH) of adifferent type are multiplexed in frequency domain, since inter-carrierinterference occurs due to spectrum emission, it may cause performancedeterioration. In order to solve the problem, it may considerintroducing a guard frequency between PBCH and PDSCH. And, in order toreduce the impact of the ICI, a network may allocate RBs fortransmitting data by separating the RBs.

However, since it is necessary to make a reservation for the manynumbers of REs as a guard frequency, the method above is not anefficient method. As a more efficient method, one or more subcarrierspositioned at an edge of a PBCH transmission bandwidth can be reservedas a guard frequency. The precise number of reserved REs can be changedaccording to subcarrier spacing of the PBCH. For example, twosubcarriers can be reserved at each edge of a PBCH transmissionbandwidth according to subcarrier spacing of 15 kHz for transmitting thePBCH. On the contrary, one subcarrier can be reserved according tosubcarrier spacing of 30 kHz for transmitting the PBCH.

Referring to FIG. 15 (a), NR-PBCH is allocated within 288 REs and theREs are configured by 24 RBs. Meanwhile, since a length of NR-PSS/NR-SSScorresponds to 127, 12 RBs are necessary for transmitting NR-PSS/NR-SSS.In particular, when an SS block is configured, the SS block is allocatedwithin 24 RBs. And, it is preferable to allocate the SS block within 24RBs to align an RB grid between numerologies different from each other(e.g., 15 kHz, 30 kHz, 60 kHz, etc.). And, since a minimum bandwidth of5 MHz capable of defining 25 RBs with 15 MHz subcarrier spacing isassumed in the NR system, 24 RBs are used to transmit an SS block. TheNR-PSS/SSS is positioned at the center of the SS block. This mayindicate that the NR-PSS/SSS is allocated to 7^(th) to 18^(th) RBs.

Meanwhile, if an SS block is configured as shown in FIG. 15 (a), aproblem may occur at an AGC (automatic gain control) operation of a UEin 120 kHz subcarrier spacing and 240 kHz subcarrier spacing. Inparticular, in case of the 120 kHz subcarrier spacing and the 240 kHzsubcarrier spacing, it may fail to properly perform detection of NR-SSSdue to the AGC operation. Hence, as described in the following twoembodiments, it may consider changing a configuration of an SS block.

(Method 1) PBCH-PSS-PBCH-SSS

(Method 2) PBCH-PSS-PBCH-SSS-PBCH

In particular, if a PBCH symbol is positioned at a starting point of anSS block and the PBCH symbol is used as a dummy symbol for an AGCoperation, it may be able to make the AGC operation of a UE to be moresmoothly performed.

Meanwhile, NR-PSS/NR-SSS/NR-PBCH can be allocated as shown in FIG. 15(b). In particular, the NR-PSS is allocated to a 0^(th) symbol and theNR-SSS can be allocated to a 2^(nd) symbol. And, the NR-PBCH can beallocated to a 1^(st) to a 3^(rd) symbol. In this case, the NR-PBCH canbe dedicatedly allocated to the 1^(st) and the 3^(rd) symbol. In otherword, the NR-PBCH is allocated to the 1^(st) symbol and the 3^(rd)symbol only and the NR-SSS and the NR-PBCH can be mapped to the 2^(nd)symbol together.

8. SS Burst Configuration

A method of determining an OFDM symbol in which an SS block istransmittable is described in the present invention. A CP type issemi-statically configured together with UE-specific signaling. AnNR-PSS/SSS can support a normal CP. By doing so, it may be able to solvea CP detection problem at the time of performing initial access.

However, in NR system, an extended CP can be included in every edge of0.5 ms. In particular, when an SS block is positioned within a slot orbetween slots, a center of the SS block can be positioned at an edge of0.5 ms. In this case, a CP of a different length can be applied toNR-PSS and/or NR-SSS in the SS block. In this case, if a UE performsNR-SS detection under the assumption that a normal CP is applied to theNR-SSS and/or the NR-SSS, detection performance can be deteriorated.Hence, it is necessary to design an SS block not to exceed 0.5 ms edgein the NR system.

FIG. 16 illustrates an example of configuring an SS burst in a TDD case.In NR system, a DL control channel is positioned at a first OFDM symbolin a slot and/or a mini slot and a UL control channel can be positionedat a lastly transmitted UL symbol. In order to avoid a collision betweenan SS block positioned in a slot and the DL/UL control channel, the SSblock can be positioned at the center of the slot.

The maximum number of SS blocks included in an SS burst set isdetermined according to a frequency range. And, a candidate value of thenumber of SS blocks is determined according to a frequency range.Meanwhile, the present invention proposes a total time spacing necessaryfor transmitting an SS block in an SS burst set based on the example ofconfiguring the SS burst show in FIG. 16.

TABLE 3 Subcarrier The maximum number of SS block Spacing 1 2 4 8 32 64 15 kHz 1 ms   1 ms 2 ms 4 ms — —  30 kHz — 0.5 ms 1 ms 2 ms — — 120 kHz— — — — 2 ms 4 ms 240 kHz — — — — 1 ms 2 ms

As shown in Table 3, if subcarrier spacing of 30 kHz and 240 kHz areintroduced to transmit NR-SS, it may be able to anticipate that an SSblock is to be transmitted within maximum 2 ms. However, since basicsubcarrier spacing for NR-SS transmission corresponds to 15 KHz and 120kHz, it is necessary to determine whether to introduce a wider minimumsystem bandwidth (e.g., 10 MHz for 20 kHz subcarrier spacing and 80 MHzfor 240 kHz subcarrier spacing) to introduce 30 kHz and 240 kHzsubcarrier spacing. If it is determined that the NR supports 5 MHz in aband equal to or narrower than 6 GHz and supports a minimum systembandwidth of 50 MHz in a band of 6 GHz, it is necessary to design an SSburst set according to 15 kHz and 120 kHz subcarrier spacing. If themaximum number of SS blocks corresponds to 8 in a band equal to ornarrower than 6 GHz and 64 in a band wider than 6 GHz, since timenecessary for transmitting an SS block corresponds to 4 ms, systemoverhead is considerably high. And, since it is preferable to have shorttime spacing in transmitting an SS block in terms of network energysaving and UE measurement, it is necessary to define a candidateposition for transmitting an SS block within duration of N ms (e.g.,N=0.5, 1, 2).

9. SS Burst Set Configuration

When an SS burst set is configured, as shown in FIG. 17, it may considertwo types according to an SS burst periodicity. One is a local typeshown in FIG. 17 (a). According to the local type, all SS blocks arecontinuously transmitted within an SS burst set. On the other hand,another one is a distribution type shown in FIG. 17 (b). According tothe distribution type, an SS burst is periodically transmitted within anSS burst set periodicity.

In the aspect of energy saving for an idle UE and efficiency formeasuring inter-frequency, an SS burst of the local type provides anadvantage compared to an SS burst of the distribution type. Hence, it ismore preferable to support the SS burst of the local type.

Meanwhile, as shown in FIG. 17 9 a), if an SS burst set is configured bythe local type, it is unable to transmit an uplink signal during asymbol period to which the SS burst set is mapped. In particular, assubcarrier spacing to which an SS block is assigned is getting bigger, asize of a symbol is getting smaller. In particular, the number of symbolperiods in which an uplink signal is not transmitted increases. Ifsubcarrier spacing to which an SS block is assigned is equal to orgreater than a certain size, it is necessary to empty a symbol outbetween SS bursts with a prescribed space to perform uplinktransmission.

FIG. 18 illustrates an SS burst set configuration when subcarrierspacing to which an SS block is assigned corresponds to 120 kHz and 240kHz. Referring to FIG. 18, when subcarrier spacing corresponds to 120kHz and 240 kHz, an SS burst is configured in a unit of 4 SS burstswhile a prescribed space is emptied out. In particular, an SS block isarranged in a unit of 0.5 ms while a symbol period (0.125 ms) forperforming uplink transmission is emptied out.

In a frequency range equal to wider than 6 GHz, subcarrier spacing of 60kHz can be used for transmitting data. In particular, as shown in FIG.19, in NR system, subcarrier spacing (e.g., 60 kHz) for transmittingdata and subcarrier spacing (e.g., 120 kHz or 240 kHz) for transmittingan SS block can be multiplexed.

Meanwhile, referring to a part represented by a box in FIG. 19, when anSS block of 120 kHz subcarrier spacing and data of 60 kHz subcarrierspacing are multiplexed, it is able to see that a collision or overlapoccurs at the SS block of 120 kHz subcarrier spacing, a GP of 60 kHzsubcarrier spacing, and a DL control region. Since it is preferable toavoid a collision between an SS block and a DL/UL control region, it isrequired to modify a configuration of an SS burst and an SS burst set.

In order to modify a configuration of an SS burst, the preset inventionproposes two embodiments.

As shown in FIG. 20, a first embodiment is to change a position of an SSburst format 1 and a position of an SS burst format 2. In particular, ifthe SS burst format 1 and the SS burst format 2 positioned in the box ofFIG. 20 are exchanged, it may be able to make a collision not to beoccurred between an SS block and a DL/UL control region. In other word,the SS burst format 1 is positioned at the forepart of 60 kHz subcarrierspacing and the SS burst format 2 is positioned at the latter part of 60kHz subcarrier spacing.

In summary, the aforementioned first embodiment can be represented asfollows.

1) 120 KHz Subcarrier Spacing

-   -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {4, 8, 16, 20, 32, 36, 44, 48}+70*n. For carrier        frequencies larger than 6 GHz, n=0, 2, 4, 6.    -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {2, 6, 18, 22, 30, 34, 46, 50}+70*n. For carrier        frequencies larger than 6 GHz, n=1, 3, 5, 7.

2) 240 KHz Subcarrier Spacing

-   -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {8, 12, 16, 20, 32, 36, 40, 44, 64, 68, 72, 76, 88, 92,        96, 100}+140*n. For carrier frequencies larger than 6 GHz, n=0,        2    -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {4, 8, 12, 16, 36, 40, 44, 48, 60, 64, 68, 72, 92, 96,        100, 104}+140*n. For carrier frequencies larger than 6 GHz, n=1,        3

As shown in FIG. 21, a second embodiment is to change a configuration ofan SS burst set. In particular, an SS burst set can be configured in amanner that a start boundary of the SS burst set is aligned (i.e.,matched) with a start boundary of 60 kHz subcarrier spacing slot.

Specifically, an SS burst is configured by locally arranged SS blocksduring 1 ms. In particular, an SS burst of 120 kHz subcarrier spacinghas 16 SS blocks and an SS burst of 240 kHz subcarrier spacing has 32 SSblocks during 1 ms. In this case, one slot is allocated as a gap betweenSS bursts on the basis of 60 kHz subcarrier spacing.

In summary, the aforementioned second embodiment can be represented asfollows.

1) 120 KHz Subcarrier Spacing

-   -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {4, 8, 16, 20}+28*n. For carrier frequencies larger than        6 GHz, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18.

2) 240 KHz Subcarrier Spacing

-   -   the first OFDM symbols of the candidate SS/PBCH blocks have        indexes {8, 12, 16, 20, 32, 36, 40, 44}+56*n. For carrier        frequencies larger than 6 GHz, n=0, 1, 2, 3, 5, 6, 7, 8.

10. Method of Indicating Actually Transmitted SS/PBCH Block within 5 msDuration

In NR system, it is able to specify a candidate position fortransmitting an SS block within an SS burst set period (e.g., 5 ms) toperform an initial access procedure. And, a position of an actuallytransmitted SS block can be notified to a connected/idle mode UE. Inthis case, a network may have flexibility in utilizing a resourceaccording to a network status. Yet, it may have different flexibility inconfiguring an SS burst set according to a configuration method ofindicating an actually used SS block. For example, if it is able to setindividual position information (e.g., a bitmap for an SS block or an SSburst) of actually transmitted SS blocks to a UE, both a localized typeand a distributed type may operate according to a network status. Theindividual position information can be included in different SIindicating measurement-related information.

And, it may be able to change a periodicity of an SS burst set accordingto a network configuration and provide information on measurementtiming/duration for a UE. When the SS burst set periodicity is changed,it is necessary to determine a candidate position in which an SS blockis to be transmitted. In order to determine a position in which an SSblock is to be transmitted, the present invention proposes twoembodiments described in the following.

(Method 1) A network may use an assumption of a candidate position for abasic periodicity.

(Method 2) A network can indicate a position in which an SS block is tobe actually transmitted within a measurement section.

In NR system, an SS burst set configuration can be designed according toa basic periodicity. When an SS burst set periodicity and measurementduration are indicated by a network, an SS burst set configuration canbe assumed by an SS burst configuration. For example, when there is noindication from a network, if a UE assumes 5 ms periodicity as an SSburst set periodicity for measurement, it may be able to configure an SSburst set for 5 ms periodicity. The SS burst set configuration can alsobe used for a basic periodicity (e.g., 20 ms) and a periodicityconfigured by a network (e.g., 5, 10, 20, 40, 80, and 160 ms).

In order to more efficiently utilize a resource for an SS burst setconfiguration, a network can indicate a position in which an SS block isto be actually transmitted within measurement duration. For example, incase of a basic periodicity, NR-SS and NR-PBCH should be transmittedwithin an SS burst set periodicity. Meanwhile, in case of a periodicitylonger than the basic periodicity, it may transmit NR-SS only for thepurpose of measurement. If a network is able to configure a position inwhich an SS block is to be actually transmitted, an unused resourceallocated to NR-PBCH can be allocated to a data/control channel. In caseof a periodicity shorter than the basic periodicity, a network selects apartial SS block from among SS blocks included in an SS burst set toconfigure an actually used SS block.

Meanwhile, the number of candidates for transmitting an SS block isrestricted according to network environment. For example, the number ofcandidates may vary depending on subcarrier spacing to which an SS blockis assigned. In this case, it may be able to inform a connected/idlemode UE of a position at which an SS block is actually transmitted.Actual transmitted SS/PBCH block indication indicating the position atwhich the SS block is actually transmitted can be used for utilizing aresource (e.g., rate matching) for a serving cell and can be used forperforming measurement related to a resource for a neighboring cell.

If a UE is able to precisely recognize a not transmitted SS block, theUE is able to recognize that the UE is able to receive other informationsuch as paging or data via a candidate resource of the SS block which isnot transmitted. For the flexibility of resource, it is necessary toprecisely indicate an SS block actually transmitted in a serving cell.

In particular, since it is unable to receive other information such aspaging or data in a resource in which an SS block is transmitted, a UEreceives a different data or a different signal via a resource in whichan SS block is not actually transmitted to increase efficiency ofresource utilization. Hence, it is necessary for the UE to recognize anSS block candidate in which an SS block is not actually transmitted.

In order to precisely indicate an SS block actually transmitted in aserving cell, it is necessary to have information on a full bitmap of 4,8, or 64 bits. In this case, a bit size included in the bitmap can bedetermined according to the maximum number of SS blocks capable of beingtransmitted in each frequency range. For example, in order to indicatean SS block actually transmitted in a period of 5 ms, a bitmap of 8 bitsis required in a frequency range ranging from 3 GHz to 6 GHz and abitmap of 64 bits is required in a frequency range equal to or widerthan 6 GHz.

Bits for indicating an SS block actually transmitted in a serving cellcan be defined by RMSI or OSI and the RMSI/OSI includes configurationinformation for data or paging. Since actual transmitted SS/PBCH blockindication is associated with a configuration for a downlink resource,the RMSI/OCI can include information on an actually transmitted SSblock.

Meanwhile, in order to measure a neighboring cell, actual transmittedSS/PBCH block indication of the neighboring cell is required. Inparticular, it is necessary to obtain time synchronization informationof the neighboring cell to measure the neighboring cell. If NR system isdesigned to allow asynchronous transmission between TRPs, although timesynchronization information of the neighboring cell is indicated,accuracy of the information may vary depending on a status. Hence, whenthe time information of the neighboring cell is indicated, it isnecessary to determine a unit of the time information as validinformation for the UE while asynchronous transmission is assumedbetween TRPs.

However, if there are many listed cells, an indicator of a full bitmaptype may excessively increase signal overhead. In order to decrease thesignaling overhead, it may consider an indicator of a variouslycompressed form. Meanwhile, in order not only to measure a neighboringcell but also to reduce signaling overhead, it may consider an indicatorof a compressed form for an indicator indicating an SS block transmittedby a serving cell. In other word, an SS block indicator described in thefollowing can be used for indicating an SS block actually transmitted ina neighboring cell and a serving cell. As mentioned in the foregoingdescription, an SS burst may correspond to a set of SS blocks includedin a slot according to each subcarrier. However, the SS burst maycorrespond to a group of the prescribed number of SS blocks irrespectiveof a slot in the following embodiment only.

One of embodiments is explained with reference to FIG. 22. Assume thatan SS burst includes 8 SS blocks. In this case, 8 SS bursts in total mayexist in a band equal to or wider than 6 GHz at which 64 SS blocks arepositioned.

In this case, SS blocks are grouped by an SS burst to compress theentire bitmap of 64 bits. It may use 8-bit information indicating an SSburst including actually transmitted SS blocks instead of 64-bit bitmapinformation. If the 8-bit bitmap information indicates an SS burst #0,the SS burst #0 can include one or more actually transmitted SS blocks.

In this case, it may consider additional information to indicate thenumber of actually transmitted SS blocks per SS burst. Each SS burst canlocally include SS blocks as many as the number of SS blocks indicatedby the additional information.

A UE combines the number of actually transmitted SS blocks per SS burstindicated by the additional information with the bitmap indicating theSS burst including the actually transmitted SS blocks to estimate theactually transmitted SS blocks.

For example, it may assume the indication shown in Table 4 in thefollowing.

TABLE 4 The number of 8 bit bitmap actually transmitted (SS/PBCH SS/PBCHblock per burst unit) SS/PBCH burst unit Full bitmap 11000001 4(11110000) (11110000) (00000000) (00000000) (00000000) (00000000)(00000000) (11110000)

According to Table 4, it is able to know that SS blocks are included inSS bursts #0, #1, and #7 via the 8-bit bitmap and it is able to knowthat 4 SS blocks are included in each SS burst via the additionalinformation. Consequently, it is able to estimate that SS blocks aretransmitted via 4 candidate positions prior to the SS bursts #0, #1, and#7.

Meanwhile, unlike the example above, if the additional information isforwarded in a bitmap form, it may be able to make a position at whichan SS block is transmitted have flexibility.

For example, information related to SS burst transmission is indicatedby a bitmap and an SS block transmitted within an SS burst can beindicated by other bits.

In particular, total 64 SS blocks are classified into 8 SS bursts (i.e.,SS block groups) and it may inform a UE of an SS burst in use bytransmitting 8-bit bitmap to the UE. When SS burst is defined as shownin FIG. 22, if the SS burst is multiplexed with a slot having subcarrierspacing of 60 kHz, it may have a merit in that a boundary between the SSburst and the slot is aligned. In particular, if on/off of the SS burstis indicated using a bitmap, a UE is able to know whether or not an SSblock is transmitted in a slot unit for all subcarrier spacing in afrequency band equal to or wider than 6 GHz.

In this case, a point different from the aforementioned example is toinform a UE of the additional information using a bitmap. In this case,since it is necessary to transmit bitmap information to 8 SS blocksincluded in each SS burst, 8 bits are required. The additionalinformation is commonly applied to all SS bursts. For example, if bitmapinformation on SS bursts indicates that an SS burst #0 and an SS burst#1 are used and additional bitmap information on SS blocks indicatesthat a first SS block and a fifth SS block are transmitted in an SSburst, since a first SS block and a fifth SS block are transmitted ineach of the SS burst #0 and the SS burst #1, the number of actuallytransmitted SS blocks becomes 4.

Meanwhile, a couple of neighboring cells may not be included in a celllist. The neighboring cells not included in the cell list use a defaultformat for an actually transmitted SS block. If the default format isused, a UE can perform measurement on the neighboring cells not includedin the cell list. In this case, the default format can be defined inadvance or can be configured by a network.

Meanwhile, if information on an SS block actually transmitted in aserving cell is collided with information on an SS block actuallytransmitted in a neighboring cell, a UE can obtain information on anactually transmitted SS block by prioritizing the information on the SSblock transmitted in the serving cell.

In particular, if information on actually transmitted SS blocks isreceived in a form of a full bitmap and a grouping form, since it ishighly probable that information in the full bitmap form is moreaccurate, the information in the full bitmap form can be preferentiallyused for receiving SS blocks.

11. Signal and Channel for Indicating Time Index

SS block time index indication is forwarded by NR-PBCH. If time indexindication is included in a part of the NR-PBCH such as NR-PBCH content,a scrambling sequence, a CRC, a redundancy version, and the like, theindication is forwarded to a UE safely. On the contrary, if the timeindex indication is included in a part of the NR-PBCH, it may haveadditional complexity in decoding NR-PBCH of a neighboring cell.Meanwhile, although it is able to perform decoding on the NR-PBCH of theneighboring cell, it is not mandatory in designing a system. And, it isnecessary to have additional discussion to determine a signal and achannel appropriate for forwarding SS block time index indication.

Since SS block time index information is going to be used as timeresource allocation reference information on an initial access-relatedchannel/signal such as system information forwarding, a PRACH preamble,and the like in a target cell, the SS block time index informationshould be safely transmitted to a UE. Meanwhile, a time index is usedfor measuring RSRP of an SS block level to measure a neighboring cell.In this case, the SS block time index information is not necessary to bevery accurate.

The present invention proposes that NR-PBCH DMRS is to be used as asignal for forwarding an SS block time index. And, the present inventionproposes that a time index indication is to be included in a part ofNR-PBCH. In this case, for example, the part of the NR-PBCH maycorrespond to a scrambling sequence, a redundancy version, and the likeof the NR-PBCH.

According to the present invention, it may be able to detect an SS blocktime index from NR-PBCH DMRS and the detected index can be checked byNR-PBCH decoding. And, in order to measure a neighboring cell, it may beable to obtain an index from NR-PBCH DMRS for the neighboring cell.

Time index indication can be configured via two embodiments described inthe following.

(Method 1) A single index method that an index is assigned to each ofall SS blocks included in an SS burst set.

(Method 2) A multi-index method that an index is assigned using acombination of an SS burst index and an SS block index.

As described in embodiment 1, if a single index method is supported, itis necessary to have many bits to express the number of all SS blockswithin an SS burst set periodicity. In this case, it is preferable for aDMRS sequence for NR-PBCH and a scrambling sequence to indicate SS blockindication.

On the contrary, as described in embodiment 2, if a multi-index methodis used, it may provide design flexibility for indicating an index. Forexample, both an SS burst index and an SS block index can be included ina single channel. And, each index can be individually transmitted via adifferent channel/signal. For example, the SS burst index can beincluded in contents of NR-PBCH or a scrambling sequence. The SS blockindex can be forwarded via a DMRS sequence of the NR-PBCH.

Meanwhile, the maximum number of SS blocks is changed within an SS burstwhich is configured according to a carrier frequency range. Inparticular, the maximum number of SS blocks in a frequency range equalto or narrower than 6 GHz corresponds to 8 and the maximum number of SSblocks in a frequency range ranging from 6 GHz to 52.6 GHz correspondsto 64.

In particular, the number of bits necessary for indicating an SS blockand the number of states necessary for indicating an SS block may varydepending on a carrier frequency range. Hence, it may consider applyingone of the embodiment 1 and the embodiment 2 according to a carrierfrequency range. For example, the single index method is applied in afrequency range equal to or narrower than 6 GHz and it may apply themulti-index method in a frequency range wider than 6 GHz.

More specifically, all of SS block time indexes can be determined by aPBCH DMRS in a frequency range equal to or narrower than 6 GHz. In thiscase, it is necessary to identify maximum 8 states using a PBCH DMRSsequence. In particular, it is necessary to have 3 bits for the SS blocktime indexes. And, the PBCH DMRS sequence can indicate 5 ms boundary(half frame indicator). In this case, in order to indicate theDMRS-based SS block time indexes and the 5 ms boundary, total 16 statesare required. In other word, it is necessary to have an additional 1 bitto indicate the 5 ms boundary in addition to 3 bits for indicating theSS block time indexes. It is not necessary to define a bit forindicating the SS block time indexes in PBCH contents in a frequencyrange equal to or narrower than 6 GHz.

Meanwhile, it may have better decoding performance by forwarding a bitindicating the SS block time indexes via NR-PBCH DMRS instead of PBCHcontents. If an additional signal is defined to indicate the SS blocktime indexes, signaling overhead for the additional signal occurs. Sincethe NR-PBCH DMRS corresponds to a sequence already defined in the NRsystem, the NR-PBCH DMRS does not generate additional signalingoverhead. Hence, if the NR-PBCH DMRS is used, it is able to preventexcessive signaling overhead.

On the contrary, in a frequency range equal to or wider than 6 GHz, apart of the SS block time indexes is indicated by the PBCH DMRS and theremaining part of the SS block time indexes is indicated by the PBCHcontents. For example, in order to indicate 64 SS block indexes intotal, maximum 8 SS block groups are grouped within an SS burst set andmaximum 8 SS blocks can be included in each of the SS block groups. Inthis case, in order to indicate the SS block groups, 3 bits are definedin the PBCH contents and SS block time indexes included in an SS blockgroup can be defined by a PBCH DMRS sequence. If it is able to assume asynchronization network in a frequency range equal to or wider than 6GHz in the NR system, it is not necessary to perform a decodingprocedure on PBCH for obtaining an SS burst index via the PBCH contents.

12. System Frame Number, Half Frame Boundary

The lower N number of bits of SFN information is forwarded via PBCHpayload and the top M number of bits of the SFN information is forwardedvia a scrambling sequence. Meanwhile, among the top M number of bits ofthe SFN information, the topmost 1 bit can be forwarded via a change ofa time/frequency position of a PBCH DMRS, an NR-SSS, or an SS block. Inaddition, information on a half radio frame (5 ms) boundary can beforwarded via a change of a time/frequency position of a PBCH DMRS, anNR-SSS, or an SS block.

Embodiment 1-1

When contents included in a specific SS block are forwarded by NR-PBCH,if the contents are changed in every 80 ms, the contents includeinformation not changed within 80 ms. For example, SFN informationincluded in PBCH contents is the same in a range of PBCH TTI (80 ms). Tothis end, lower 7-bit information among 10-bit SFN information isincluded in the PBCH contents. The top 3-bit information indicating aframe boundary (10 ms) can be included in a PBCH scrambling sequence.

Embodiment 1-2

When contents included in a specific SS block are forwarded by NR-PBCH,if the contents are changed in every 80 ms, the contents includeinformation not changed within 80 ms. For example, SFN informationincluded in PBCH contents is the same in a range of PBCH TTI (80 ms). Tothis end, lower 7-bit information among 10-bit SFN information isincluded in the PBCH contents. The lower 2-bit information among the top3-bit information indicating a frame boundary (10 ms) can be included ina PBCH scrambling sequence and the topmost 1-bit information istransmitted using such a signal or a channel distinguished from PBCHchannel coding as PBCH contents, a CRC, a scrambling sequence, and thelike. For example, it may use the PBCH DMRS as a signal distinguishedfrom PBCH channel coding. It may use such information as a DMRSsequence, a DMRS RE position, DMRS sequence to RE mapping change, asymbol position change in an SS block, a frequency position change of anSS block and the like.

Specifically, in case of using a DMRS sequence, it may consider a methodof using a phase difference (e.g., orthogonal code cover) between twoOFDM symbols in which a DMRS is transmitted. And, in case of using aDMRS sequence, it may consider a method of changing an initial value.Specifically, when 2 m-sequences are used for a gold sequence, if aninitial value of one m-sequence is fixed and an initial value of anotherm-sequence is changed using a cell-ID and other information, it may beable to introduce a method of changing an initial value usinginformation to be transmitted to the m-sequence using the fixed initialvalue.

More specifically, if a different initial value (e.g., [0 1 0 . . . 0]is additionally introduced to a legacy fixed initial value (e.g., [1 0 0. . . 0]) according to 1 bit indicating 10 ms boundary information, twoinitial values can be changed in a unit of 10 ms in a range of 20 ms. Asa different method, one m-sequence uses a fixed initial value as it isand another m-sequence may add information to be transmitted to aninitial value.

In case of using a DMRS RE position, it may apply a V-shift method thatchanges a frequency axis position of a DMRS according to information.Specifically, when 0 ms and 10 ms are transmitted in a range of 20 ms,an RE position is differently arranged. In this case, when a DMRS isarranged in every 4 REs, it may introduce a method of shifting the DMRSin a unit of 2 REs.

And, it may be able to apply a method of changing a scheme of mapping aPBCH DMRS sequence to an RE. Specifically, in case of 0 ms, a sequenceis preferentially mapped to a first RE. In case of 10 ms, a sequence ismapped using a different mapping method. For example, an oppositesequence is mapped to a first RE, a sequence is preferentially mapped toa median RE of a first OFDM symbol, or a sequence is preferentiallymapped to a first RE of a second OFDM symbol. And, it may consider amethod of changing an arrangement order such as PSS-PBCH-SSS-PBCH in anSS block with a different arrangement. For example, while such anarrangement as PBCH-PSS-SSS-PBCH is basically applied, it may apply adifferent arrangement in 0 ms and 10 ms. And, it may apply a method ofchanging an RE position to which PBCH data is mapped in an SS block.

Embodiment 1-3

1 bit information indicating a half frame boundary can be transmittedusing such a signal or a channel distinguished from a part related toPBCH channel coding as PBCH contents, a CRC, a scrambling sequence, andthe like. For example, similar to the embodiment 2, it may use the PBCHDMRS as a signal distinguished from PBCH channel coding. It may use suchinformation as a DMRS sequence, a DMRS RE position, DMRS sequence to REmapping change, a symbol position change in an SS block, a frequencyposition change of an SS block and the like. In particular, it may applythe information when change is made at 0 ms and 5 ms in a range of 10ms.

In addition, for time change information in a unit of 5 ms in a range of20 ms including half frame boundary information and SFN top 1 bitinformation, as mentioned earlier in the embodiment 2, it may use suchinformation as a DMRS sequence, a DMRS RE position, DMRS sequence to REmapping change, a symbol position change in an SS block, a frequencyposition change of an SS block and the like. In particular, it may applythe information when time information is changes at 0, 5, 10, and 15 msin a range of 20 ms.

Embodiment 1-4

When a PBCH is configured by the total N number of REs, if the M (<N)number of REs are allocated to transmit PBCH data and QPSK modulation isused, a length of a scrambling sequence becomes 2*M. The L number ofscrambling sequences can be generated by generating a long sequence of alength of L*2*M and dividing the long sequence by a unit of 2*M. As ascrambling sequence, it may use a PN sequence, a gold sequence, and an Msequence. Specifically, it may use a gold sequence of a length of 31. Acell ID is used for initializing the PN sequence and an SS block indexobtained from a PBCH DMRS can be additionally used for initializing thePN sequence. When a slot number and an OFDM symbol are derived from anSS block index, it may use a slot number/OFDM symbol number. Inaddition, half radio frame boundary information can be used as aninitialization value. If it is able to obtain a partial bit of SFNinformation using a signal or a channel distinguished from channelcoding such as contents, a scrambling sequence, and the like, the SFNinformation can be used as an initialization value of a scramblingsequence.

A length of a scrambling sequence is determined according to a length ofa bit forwarded via the scrambling sequence among the SFN information.For example, if 3-bit information of the SFN information is forwardedvia a scrambling sequence, it is necessary to represent 8 states usingthe information. To this end, a sequence of a length of 8*2*M isrequired. Similarly, when 2-bit information is forward, a sequence of alength of 2*2*M is required.

A bit string in which PBCH contents and a CRC are included is codedusing a polar code to generate coded bits of a length of 512. A codedbit is shorter than a length of a scrambling sequence. A coded bit of alength of 512 is repeated several times to generate a bit string of alength identical to a length of a scrambling sequence. Subsequently, therepeated coded bit and a scrambling sequence are multiplied and QPSKmodulation is performed. The modulated symbol is divided by a unit of alength M and is mapped to a PBCH RE.

For example, referring to FIG. 24, when 3-bit information of SFNinformation is forwarded via a scrambling sequence, in order to changethe scrambling sequence in every 10 ms, a modulated symbol sequence in aunit of a length M is transmitted in a unit of 10 ms. In this case, eachof modulation symbols transmitted in a unit of 10 ms is different. If aperiodicity of an SS burst set corresponds to 5 ms, the same modulatedsymbol sequence is transmitted during two transmission periods includedin a range of 10 ms. If a UE is able to obtain half radio frame (5 ms)boundary information, the UE is able to combine information of PBCHwhich are transmitted twice in a range of 10 ms. In order to find out 8scrambling sequences, which are transmitted in a unit of 10 ms in arange of 80 ms, the UE performs blind decoding 8 times in total. In thiscase, the UE performs decoding on a different channel rather than PBCHto obtain half frame boundary 1-bit information (e.g., C₀). Then, the UEperforms blind decoding on PBCH to obtain the first N-bit information ofSFN (e.g., S₀, S₁, and S₂) and obtains SFN information (e.g., S₃ to S₉)corresponding to the remaining 10-N bit from PBCH contents. Hence, theUE can configure SFN information of 10 bits in total.

As a different example, when 3-bit information of SFN information isforwarded via a scrambling sequence and half frame boundary informationis included in PBCH contents, the same contents are included in 10 mstransmission periodicity. However, since PBCH contents including anoffset of 5 ms have different half frame boundary information of 1 bit,different contents can be transmitted in every 5 ms. In particular,contents of two types are configured due to the half frame boundaryinformation of 1 bit. A base station encodes each of the contents of twotypes and performs bit repetition, scrambling, modulation, and the likeon each of the contents.

If a UE fails to obtain 5 ms boundary information, it is difficult forthe UE to combine signals transmitted in every 5 ms. Instead, the UEidentically performs decoding 8 times, which are performed in every 10ms, in 5 ms offset. In particular, the UE performs decoding at least 8times to obtain first N-bits information (e.g., S₀, S₁, and S₂) of SFNand obtains SFN information (e.g., S₃ to S₉) corresponding to theremaining 10-N bits from PBCH contents. Moreover, the UE obtains halfradio frame boundary 1 bit information (e.g., C₀). In other word, the UEobtains time information in a unit of 5 ms by configuring the obtainedbit information.

Similarly, if 2-bit information of the SFN information is forwarded viaa scrambling sequence, the scrambling sequence is changed in every 20 msand the same modulated symbol sequence is transmitted during four 5 mstransmission periods included in a range of 20 ms. If a UE is able toobtain half radio frame boundary information and the top 1-bitinformation of the SFN, the UE is able to combine information of PBCHwhich are received in a range of 20 ms. The UE performs blind decoding 4times in every 20 ms. In this case, reception complexity of the UEincreases due to the half frame boundary information and the top 1-bitinformation of the SFN obtained by the UE. However, since it is able toreduce complexity of PBCH blind decoding and perform PBCH combination asmany as 16 times, it may expect the enhancement of detectionperformance. In this case, the UE performs decoding on a differentchannel rather than PBCH to obtain half frame boundary 1-bit information(e.g., C₀) and the top 1-bit information (e.g., S₀) of the SFN.

The UE performs blind decoding on PBCH to obtain the first (N−1)-bitinformation (e.g., S1 and S₂) of SFN after the top 1-bit and obtains SFNinformation (e.g., S₃ to S₉) corresponding to the remaining 10-N bitfrom PBCH contents. Hence, the UE can configure half radio frameboundary information (C₀) and SFN information (e.g., S₀ to S₉) of 10bits in total. The obtained time information provides a unit of 5 ms. Inthis case, a plurality of SS blocks can be transmitted in a range of 5ms. An SS block position in the range of 5 ms can be obtained from aPBCH DMRS and PBCH contents.

13. SS Block Time Index

The present invention proposes a method of configuring an SS burst setwithin shorter duration (e.g., 2 ms) to save energy of a network and aUE. In this case, all SS blocks can be positioned within an SS burst setperiodicity irrespective of a periodicity (e.g., 5, 10, 20, 40, 80, 160ms). FIG. 23 illustrates an SS block index when subcarrier spacingcorresponds to 15 kHz.

An SS block index is explained with reference to FIG. 23. If the maximumnumber of SS blocks is defined by L, indexes of SS blocks correspond to0 to L−1. And, the SS block indexes are derived from OFDM symbol indexesand slot indexes. And, an SS burst set can be configured by 4 SS blockspositioned at two slots adjacent to each other. Hence, the SS blockindexes correspond to 0 to 3 and the slot indexes are defined by 0and 1. And, an SS block includes 4 OFDM symbols and two OFDM symbolsincluded in the SS block are used to transmit PBCH. In this case,indexes of the OFDM symbols for transmitting the PBCH may correspond to0 and 2. As shown in FIG. 23 (a), indexes of an SS block are derivedfrom indexes of an OFDM symbol and a slot. For example, an SS blocktransmitted in a slot #1 and an OFDM symbol #2 is mapped to an index 3.

As shown in FIG. 23 (b), a network can configure a periodicity of an SSburst set in NR system. And, it may be able to configure a shortperiodicity such as 5 and 10 ms. By doing so, it may be able to allocatemore SS block transmissions. An index of an SS block can be identifiedwithin a configured periodicity of an SS burst set. As shown in FIG. 23(c), if a periodicity of 5 ms is configured, it may be able to transmit4 SS blocks within the configured periodicity. And, it may be able totransmit 16 SS blocks in total within a basic periodicity. In this case,indexes of the SS blocks can be repeated within a default periodicityand 4 SS blocks among the 16 SS blocks may have the same index.

A method of indicating SS block time indexes is explained in moredetail.

A part of the SS block time indexes is forwarded via a sequence of aPBCH DMRS and the remaining indexes are forwarded via PBCH payload. Inthis case, the SS block time indexes forwarded via the PBCH DMRSsequence correspond to information of N-bits and the SS block timeindexes forwarded via the PBCH payload correspond to information ofM-bits. When the maximum number of SS blocks in a frequency rangecorresponds to L-bits, the L-bits correspond to the sum of M-bit andN-bits. Assume that H (=2{circumflex over ( )}L) states capable of beingforwarded in a range of 5 ms correspond to a group A, J (=2{circumflexover ( )}N) states capable of being forwarded by a PBCH DMRS andrepresented by N-bits correspond to a group B, and I (=2{circumflex over( )}M) states capable of being forwarded by PBCH payload and representedby M-bits correspond to a group C, the H number of states of the group Acan be represented by multiplication of the J number of states of thegroup B and the I number of states of the group C. In this case, themaximum P (P is 1 or 2) number of states belonging to either the group Bor the group C can be represented in a range of 0.5 ms. Meanwhile, thenames of the groups described in the present invention are used forclarity. The names can be represented in various ways.

Meanwhile, the number of states forwarded via a PBCH DMRS sequence maycorrespond to 4 in a frequency range equal to or narrower than 3 GHz, 8in a frequency range ranging from 3 GHz to 6 GHz, and 8 in a frequencyrange equal to or wider than 6 GHz. In a band equal to or narrower than6 GHz, 15 kHz subcarrier spacing and 30 kHz subcarrier spacing are used.In this case, if the 15 kHz subcarrier spacing is used, maximum 1 stateis included in a range of 0.5 ms. If the 30 kHz subcarrier spacing isused, maximum 2 states are included in a range of 0.5 ms. In a bandequal to or wider than 6 GHz, 120 kHz subcarrier spacing and 240 kHzsubcarrier spacing are used. In this case, if the 120 kHz subcarrierspacing is used, maximum 1 state is included in a range of 0.5 ms. Ifthe 240 kHz subcarrier spacing is used, maximum 2 states are included ina range of 0.5 ms.

FIGS. 25 (a) and (b) illustrate SS blocks included in a range of 0.5 mswhen 15/30 kHz subcarrier spacing is used and 120/240 kHz subcarrierspacing is used, respectively. As shown in FIG. 29, in case of using the15 kHz subcarrier spacing, 1 SS block is included in a range of 0.5 ms.In case of using the 30 kHz subcarrier spacing, 2 SS blocks are includedin a range of 0.5 ms. In case of using the 120 kHz subcarrier spacing, 8SS blocks are included in a range of 0.5 ms. In case of using the 240kHz subcarrier spacing, 16 SS blocks are included in a range of 0.5 ms.

In case of using the 15 kHz and 30 kHz subcarrier spacing, an index ofan SS block included in a range of 0.5 ms can be mapped to an indextransmitted via a PBCH DMRS sequence by one-to-one (1:1). An indicatorbit for indicating an SS block index can be included in PBCH payload. Ina band equal to narrower than 6 GHz, the bit can be comprehended asinformation of a different purpose without being comprehended as a bitfor indicating an SS block index. For example, the indicator bit can beused for expanding coverage. The information bit can be used forforwarding a signal associated with an SS block or a repetition count ofa resource.

When a PBCH DMRS sequence is initialized by a cell ID and an SS blockindex, in case of using 15 kHz and 30 kHz subcarrier spacing, an SSblock index transmitted in a range of 5 ms can be used as an initialvalue of the sequence. In this case, the SS block index may correspondto an SSBID.

Embodiment 2-1

In case of using 120 kHz subcarrier spacing, the number of SS blockindexes included in a range of 0.5 ms corresponds to 8. In the range of0.5 ms, a PBCH DMRS sequence is the same and PBCH payload may changeaccording to an SS block index. However, when a first SS block group istransmitted in a 0.5 ms section, it may use a different PBCH DMRSsequence different from a sequence used by a second SS block group in a0.5 ms section. In this case, the second SS block group can betransmitted prior to the first SS block group. In order to identify anSS block transmitted in a different 0.5 ms section, an SS block indexfor an SS block group is forwarded via PBCH payload.

In case of using 240 kHz subcarrier spacing, the number of SS blockindexes included in a range of 0.5 ms corresponds to 16. In the range of0.5 ms, the number of PBCH DMRS sequences may correspond to 2. Inparticular, a PBCH DMRS sequence used for 8 SS blocks within the first0.5 ms may be different from a PBCH DMRS sequence used for 8 SS blockswithin the second 0.5 ms. The SS block indexes are forwarded in PBCHpayload included in the SS blocks of the first and the second 0.5 ms.

In particular, it may be able to apply a method of consistentlymaintaining a PBCH DMRS sequence during a prescribed time period. When aUE attempts to detect a signal of a neighboring cell to secure timeinformation of the neighboring cell, if a PBCH DMRS sequence-based timeinformation forwarding method having low detection complexity and betterdetection performance is applied, it may have a merit in that it is ableto obtain time information having accuracy as accurate as 0.5 ms or 0.25ms. In particular, it is able to provide time accuracy as accurate as0.25 ms or 0.5 ms irrespective of a frequency range.

Embodiment 2-2

In case of using 120 kHz subcarrier spacing, the number of SS blockindexes included in a range of 0.5 ms corresponds to 8. In the range of0.5 ms, an SS block index included in PBCH payload is the same and aPBCH DMRS sequence may change according to an SS block index. However,when a first SS block group is transmitted in a 0.5 ms section, it mayuse a different SS block index forwarded via PBCH payload different froma sequence used by a second SS block group in a 0.5 ms section. In thiscase, the second SS block group can be transmitted prior to the first SSblock group.

In case of using 240 kHz subcarrier spacing, the number of SS blockindexes included in a range of 0.5 ms corresponds to 16. In the range of0.5 ms, the number of SS block indexes forwarded via PBCH payload maycorrespond to 2. In particular, SS block indexes, which are included inPBCH payload, transmitted from 8 SS blocks within the first 0.5 ms arethe same and 8 SS block indexes in the second 0.5 ms are different fromthe SS block index of the first 0.5 ms. In this case, the PBCH DMRSincluded in each of the first part and the second part uses sequencesdistinguished from each other according to an SS block index.

In case of using 120 kHz subcarrier spacing and 240 kHz subcarrierspacing, an SS block index is represented by combining indexes obtainedfrom two paths. The first embodiment and the second embodiment can beexpressed by an equation 7 and an equation 8 in the following.

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Floor(SS-PBCH block index/P)

SSBGID=Mod(SS-PBCH block index,P)  [Equation7]

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Mod(SS-PBCH block index,P)

SSBGID=Floor(SS-PBCH block index/P)  [Equation 8]

In this case, P can be represented by 2{circumflex over ( )} (number ofbits forwarded via PBCH DMRS)

In the foregoing description, for clarity, a specific number (e.g., 4 or8) is used. This is just an example only. The present invention is notrestricted to the specific number. For example, the number can bedetermined according to the number of information bits forwarded via aPBCH DMRS. If information of 2 bits is forwarded via the PBCH DMRS, anSS block group can be configured by 4 SS blocks. The SS block time indexforwarding scheme mentioned earlier in the 120/240 kHz subcarrierspacing can also be applied to the 15/30 kHz subcarrier spacing.

Examples of bit configuration of time information and a forwarding pathof the information mentioned earlier in “12. System Frame Number, Halfframe boundary” and “13. SS block time index” can be summarized asfollows with reference to FIG. 24.

-   -   7 bits among SFN 10 bits and SS block group index 3 bits are        forwarded via PBCH contents    -   20 ms boundary information 2 bits (S2, S1) are forwarded via PCH        scrambling    -   5 ms boundary information 1 bit (C0) and 10 ms boundary        information 1 bit (S0) are forwarded via DMRS RE position shift,        phase difference between DMRSs of OFDM symbol including PBCH,        change of a method of mapping DMRS sequence to RE, change of        PBCH DMRS sequence initial value, etc.    -   SS block index indication information 3 bits (B2, B1, B0) are        forwarded via DMRS sequence

14. NR-PBCH Contents

In NR system, it is anticipated that a payload size of MIB is to beextended based on a response LS of RAN2. The MIB payload size andNR-PBCH contents anticipated in the NR system are described in thefollowing.

1) Payload: 64 bits (48-bit information, 16-bit CRC)

2) NR-PBCH contents:

-   -   At least a part of SFN/H-SFN    -   Configuration information on common search space    -   Center frequency information of NR carrier

A UE detects a cell ID and timing information and may be then able toobtain information for accessing a network from PBCH including a part oftiming information such as SFN, an SS block index, and half frametiming, information on a common control channel such as a time/frequencyposition, information on a bandwidth part such as a bandwidth and an SSblock position, and information on an SS burst set such as an SS burstset periodicity and an actually transmitted SS block index.

Since limited time/frequency resources such as 576 REs are occupied onlyfor PBCH, essential information should be included in the PBCH. And, ifpossible, it may use such an auxiliary signal as a PBCH DMRS to furtherinclude essential information or additional information.

(1) SFN (System Frame Number)

In NR system, a system frame number (SFN) is defined to identify 10 msspace. And, similar to LTE system, it may introduce indexes between 0and 1023 for the SFN. The indexes can be explicitly indicated using abit or can be implicitly indicated.

According to the NR system, a PBCH TTI corresponds to 80 ms and aminimum SS burst periodicity corresponds to 5 ms. Hence, PBCH as much as16 times can be transmitted in a unit of 80 ms. A different scramblingsequence for each transmission can be applied to a PBCH coded bit.Similar to an LTE PBCH decoding operation, a UE can detect 10 ms space.In this case, 8 states of the SFN are implicitly indicated by a PBCHscrambling sequence and 7 bits for representing the SFN can be definedin the PBCH contents.

(2) Timing Information in Radio Frame

An SS block index can be explicitly indicated by a bit included in aPBCH DMRS sequence and/or PBCH contents according to a carrier frequencyrange. For example, in a frequency range equal to or narrower than 6GHz, 3 bits of SS block indexes are forwarded via a PBCH DMRS sequenceonly. In a frequency band equal to or wider than 6 GHz, lowest 3 bits ofSS block indexes are indicated by a PBCH DMRS sequence and top 3 bits ofSS block indexes are forwarded by PBCH contents. In particular, maximum3 bits for SS block indexes can be defined in the PBCH contents in afrequency range ranging from 6 GHz to 52.6 GHz only.

And, a boundary of a half frame can be forwarded by a PBCH DMRSsequence. In particular, in a frequency range equal to or narrower than3 GHz, if a half frame indicator is included in a PBCH DMRS, it may havebetter performance compared to a case that the half frame indicator isincluded in the PBCH contents. In particular, since FDD scheme is mainlyused in a frequency range equal to or narrower than 3 GHz, a level oftime synchronization mismatched between subframes or slots may be high.Hence, in order to more precisely match the time synchronization, it ispreferable to forward the half frame indicator via the PBCH DMRS havingbetter decoding performance instead of the PBCH contents.

However, in a frequency range wider than 3 GHz, since TDD scheme is notused a lot, a level of time synchronization mismatched between subframesor slots is not high. Hence, although the half frame indicator isforwarded via the PBCH contents, it may have fewer disadvantages.

Meanwhile, the half frame indicator can be forwarded via both the PBCHDMRS and the PBCH contents.

(3) Number of OFDM Symbols Included in Slot

In relation to the number of OFDM symbols included in a slot in acarrier frequency range equal to or narrower than 6 GHz, NR considers aslot including 7 OFDM symbols and a slot including 14 OFDM symbols. Ifthe NR determines to support the slots of two types, it is necessary todefine a method of displaying a slot type to display a time resource ofCORESET.

(4) Information for Identifying that there is No RMSI Corresponding toPBCH

In NR, an SS block can be used not only for providing information foraccessing a network but also for measuring an operation. In particular,in order to perform a broadband CC operation, it may be able to transmitmultiple SS blocks for measurement.

However, it is not necessary to forward RMSI via all frequency positionsat which an SS block is transmitted. In particular, it is able toforward the RMSI via a specific frequency position for efficiency ofresource utilization. In this case, UEs performing an initial accessprocedure are unable to recognize whether or not RMSI is provided at adetected frequency position. In order to solve the problem above, it isnecessary to define a bit field for identifying that there is no RMSIcorresponding to PBCH of a detected frequency region. Meanwhile, it isalso necessary to consider a method capable of identifying that there isno RMSI corresponding to PBCH without the bit field.

To this end, an SS block in which RMSI does not exist is configured tobe transmitted at a frequency position which is not defined as afrequency raster. In this case, since UEs performing an initial accessprocedure are unable to detect the SS block, it is able to solve theaforementioned problem.

(5) SS Burst Set Periodicity and Actually Transmitted SS Block

It is able to indicate information on an SS burst set periodicity and anactually transmitted SS block for the purpose of measurement. Inparticular, it is preferable to include the information in systeminformation for cell measurement and inter/intra cell measurement. Inparticular, it is necessary to define the information in PBCH contents.

(6) Bandwidth-Related Information

A UE attempts to detect a signal from an SS block bandwidth while aninitial synchronization procedure including a cell ID detection and PBCHdecoding is performed. Subsequently, the UE obtains system informationusing a bandwidth indicated by a network via PBCH contents and cancontinuously perform the initial access procedure to perform a RACHprocedure. A bandwidth can be defined to perform the initial accessprocedure. It may be able to define CORSET, RNSI, OSI, and a frequencyresource for RACH message in a bandwidth for a downlink common channel.And, an SS block can be positioned as a part of the bandwidth for thedownlink common channel. In summary, the bandwidth for the downlinkcommon channel can be defined in PBCH contents. Display of a relativefrequency position between a bandwidth for an SS block and the bandwidthfor the downlink common channel can be defined in the PBCH contents. Inorder to simplify the display of the relative frequency position, aplurality of bandwidths for an SS block can be regarded as candidatepositions at which the SS block is positioned in the bandwidth for thedownlink common channel.

(7) Numerology Information

When an SS block is transmitted, 15, 30, 120, or 240 kHz subcarrierspacing is used. Meanwhile, when a data is transmitted, 15, 30, 60, or120 kHz subcarrier spacing s used. When an SS block, CORESET, and RMSIare transmitted, it may use the same subcarrier spacing. If RAN1 checksinformation on the subcarrier spacing, it is not necessary to definenumerology information.

On the contrary, it may consider the possibility of changing subcarrierspacing for CORESET and RMSI. In RAN4, if 15 subcarrier spacing areapplied to SS block transmission only according to the agreement for acarrier minimum bandwidth, after PBCH is decoded, it may be necessary tochange subcarrier spacing into 30 kHz for a next procedure. And, when240 kHz subcarrier spacing is used for transmitting an SS block, sincethe 240 kHz subcarrier spacing is not defined for data transmission, itis necessary to change subcarrier spacing to transmit data. If RAN 1 isable to change subcarrier spacing to transmit data via PBCH contents, itmay be able to define 1-bit indicator for the data transmission. The1-bit indicator can be comprehended as {15, 30 kHz} or {60, 120 kHz}according to a carrier frequency range. And, indicated subcarrierspacing can be regarded as reference numerology for an RB grid.

(8) Payload Size

As shown in Table 5, maximum 64-bit payload size can be assumed inconsideration of decoding performance of PBCH.

TABLE 5 Bit size Details 6 GHz  

  6 GHz  

  System Frame Number (MSB) 7 7 SS/PBCH block time index (MSB) 0 3Reference numerology [1] [1] Bandwidth for DL common channel, [3] [2]and SS block position # of OFDM symbols in a Slot [1] 0 CORESET About[10] About [10] (Frequency resource-bandwidth, location) (Timeresource-starting OFDM symbol, Duration)  

 E Monitoring Periodicity, offset, duration) Reserved Bit [20]  [20] CRS 16 + a 16 + a Total 64  64 

indicates data missing or illegible when filed

15. NR-PBCH Scrambling

A type of NR-PBCH scrambling sequence and sequence initialization aredescribed. In NR, it may consider using a PN sequence. However, if agold sequence of a length of 31 defined in LTE system is used as anNR-PBCH sequence and a serious problem does not occur, it is preferableto reuse the gold sequence as the NR-PBCH scrambling sequence.

A scrambling sequence can be initialized by a cell ID and 3 bits of SSblock indexes indicated by PBCH-DMRS can be used for initializing ascrambling sequence. And, if half frame indication is indicated by aPBCH-DMRS or a different signal, the half frame indication can also beused as a seed value for initializing a scrambling sequence.

16. PBCH Coding Chain Configuration and PBCH DMRS Transmission Scheme

Embodiments for a PBCH coding chain configuration and a PBCH DMRStransmission scheme are explained in the following with reference toFIG. 26.

First of all, CORESET information and MIB configuration may varyaccording to an SS block and an SS block group index, respectively.Hence, encoding is performed on MIB according to an SS block. In thiscase, a size of a coded bit corresponds to 3456 bits. Since a size of apolar code output bit corresponds to 512 bits, the polar code output bitcan be repeated 6.75 times (512*6+384).

A scrambling sequence of a length of 3456 is multiplied by the repeatedbit. The scrambling sequence is initialized by a cell ID and an SS blockindex forwarded via a DMRS. The scrambling sequence of the length of3456 bits is equally divided into 4 part each of which has 864 bits andQPSK modulation is performed on each part to configure a set of 4modulated symbols each of which has a length of 432 bits.

A new modulated symbol set is transmitted in every 20 ms and the samemodulated symbol set can be repeated maximum 4 times within 20 ms. Inthis case, in a section in which the same modulated symbol set isrepeated, a frequency axis position of a PBCH DMRS is changed accordingto a cell ID. In particular, a position of a DMRS is shifted in every0/5/10/15 ms according to equation 9 described in the following.

vshift=(vshift_cell+vshift_frame)mod 4,vshift_cell=Cell-ID mod 3,vshift_frame=0,1,2,3  [Equation 9]

A PBCH DMRS sequence uses a gold sequence of a length of 31. An initialvalue of a first m-sequence is fixed by a single value and, as shown inequation 10, an initial value of a second m-sequence is determined basedon an SS block index and a cell ID.

c _(init)=2¹⁰*(SSBID+1)*(2*CellID+1)+CellID  [Equation 10]

If contents of SS blocks are the same, channel coding and repetition ofa bit are performed on a single SS block only. And, if it is assumedthat a different value is applied to a scrambling sequence according toan SS block, bits are segmented from a procedure of generating andmultiplying the scrambling sequence and a modulation procedure isperformed according to an SS block.

In the following, an operation of a base station and an operation of aUE are explained according to a scheme of forwarding half radio frameinformation and SFN top 1 bit. In the following description, C0 and S0correspond to a half frame boundary and a frame boundary indication bit,respectively.

(1) C0 and S0 are forwarded via CRC:

This information corresponds to information changed in every 0, 5, 10,15 ms. Since 4 types of CRCs are generated, encoding is performed 4times. Each coded bit is repeatedly arranged under the assumption thateach coded bit is transmitted 4 times in total in every 20 ms and ascrambling sequence is multiplied.

When a UE receives information, in order for the UE to combine theinformation received in every 0.5, 10, 15 ms, it is necessary for the UEto further perform blind decoding. If blind decoding is performed onPBCHs received in every 20 ms only, there is no additional complexity.However, since it is unable to combine signals transmitted in every 5ms, it may have a demerit in that it is difficult to guarantee maximumperformance.

(2) C0 and S0 are forwarded via PBCH scrambling:

Encoding is performed using one information bit and a CRC. A coded bitis repeatedly arranged under the assumption that each coded bit istransmitted 16 times in total in every 5 ms and a scrambling sequence ismultiplied. If the scheme above is used, it may have a problem that ablind decoding count is increased to 16.

(3) C0 and S0 are forwarded via DMRS sequence:

According to the present scheme, 5 bits are forwarded via a sequence ofa length of 144. Encoding is performed using one information and a CRC.A scrambling scheme has two types.

1) A coded bit is repeatedly arranged under the assumption that eachcoded bit is transmitted 16 times in total in every 5 ms and ascrambling sequence is multiplied. In this case, since a scramblingsequence is changed in every 5 ms, ICI randomization of PBCH may occur.And, since a UE obtains C0 and S0 information from a DMRS sequence, theUE is able to obtain scrambling sequence information which is changed inevery 0, 5, 10, 15 ms. And, when PBCH decoding is performed, a blinddecoding count does not increase. According to the present method, sincesignals transmitted in every 5 ms are combined, it may expect maximumperformance.

2) A coded bit is repeatedly arranged under the assumption that eachcoded bit is transmitted 4 times in total in every 20 ms and ascrambling sequence is multiplied. By doing so, it may be able to reduceICI randomization. And, a blind decoding count of a UE does not increaseand it may expect performance enhancement. And, acquisition time can beenhanced.

However, if C0 and S0 are forwarded via a DMRS sequence, since it isnecessary to include a plurality of bits in the DMRS sequence, detectionperformance can be degraded and a blind detection count may increase. Inorder to overcome the problems, it is necessary to perform combinationseveral times.

(4) C1 and S0 are forwarded via DMRS position:

The present method is basically same with the method of forwarding C0and S0 via a DMRS sequence. However, in order to forward the C0 and theS0 via a DMRS position, the position is determined based on a cell IDand a frequency position is shifted according to 0, 5, 10, 15 ms. Aneighboring cell can also perform the shift using the same method. Inparticular, if power boosting is performed on a DMRS, performance can beenhanced more.

17. Transmission Method and Antenna Port

In NR system, NR-PBCH transmission is performed based on a singleantenna port. When the transmission is performed based on a singleantenna port, it may consider methods described in the following totransmit NR-PBCH.

(Method 1) TD-PVS (time domain precoding vector switching) method

(Method 2) CDD (cyclic delay diversity) method

(Method 3) FD-PVS (frequency domain precoding vector switching) method

According to the transmission methods, NR-PBCH can obtain a transmissiondiversity gain and/or a channel estimation performance gain. Meanwhile,it may consider the TD-PVS and the CDD to transmit NR-PBCH. On the otherhand, since the FD-PVS causes overall performance loss due to a channelestimation loss, it is not preferable.

And, antenna port assumption for NR-SS and NR-PBCH is explained. In aninitial access state, it may consider transmitting NR-SS and NR-PBCH viaa different antenna port to provide network flexibility in transmittingthe NR-SS and the NR-PBCH in NR system. However, a UE may assume thatantenna ports of the NR-SS and the NR-PBCH are identical to each otheror different from each other based on a network configuration.

18. NR-PBCH DMRS Design

In NR system, a DMRS is introduced for phase reference of NR-PBCH. And,NR-PSS/NR-SSS/NR-PBCH exists in all SS blocks and OFDM symbol at whichthe NR-PSS/NR-SSS/NR-PBCH is positioned is consecutive in a single SSblock. However, if a transmission scheme is different between NR-SSS andNR-PBCH, it is unable to assume that the NR-SSS is going to be used as areference signal for demodulating the NR-PBCH. Hence, it is necessary todesign the NR-PBCH under the assumption that the NR-SSS is not used as areference signal for demodulating the NR-PBCH in NR system.

In order to design a DMRS, it is necessary to consider DMRS overhead, atime/frequency position, and a scrambling sequence.

Overall PBCH decoding performance can be determined by channelestimation performance and an NR-PBCH coding rate. The number of REs fortransmitting a DMRS has a trade-off relation between the channelestimation performance and the NR-PBCH coding rate. Hence, it isnecessary to find out the number of REs appropriate for the DMRS. Forexample, if 4 REs per RB are allocated to a DMRS, it may have betterperformance. If two OFDM symbols are allocated to transmit NR-PBCH, 192REs are used for a DMRS and 384 REs are used for MIB transmission. Inthis case, if a payload size corresponds to 64 bits, it may obtain 1/12coding speed identical to coding speed of LTE PBCH.

When multiple OFDM symbols are allocated to transmit NR-PBCH, it isnecessary to determine an OFDM symbol in which a DMRS is to be included.In this case, in order to prevent performance deterioration due to aresidual frequency offset, it is preferable to arrange a DMRS to allOFDM symbols at which the NR-PBCH is positioned. In particular, all OFDMsymbol for transmitting the NR-PBCH can include a DMRS.

A PBCH DMRS is used as a time/frequency tracking RS for an OFDM symbolposition at which NR-PBCH is transmitted. As a distance between two OFDMsymbols including a DMRS is getting longer, it is more profitable forprecisely tracking a frequency. Hence, a first OFDM symbol and a fourthOFDM symbol can be allocated to transmit NR-PBCH.

And, a frequency position of a DMRS can be mapped by interleaving intime domain capable of being shifted according to a cell ID. When DMRSpatterns are uniformly distributed, the DMRS patterns can be used forDFT-based channel estimation that provides optimized performance to 1-Dchannel estimation. In order to increase channel estimation performance,it may use broadband RB bundling.

A DMRS sequence can use a pseudo random sequence defined by a type of agold sequence. A length of a DMRS sequence can be defined by the numberof REs for a DMRS according to an SS block. And, the DMRS sequence canbe generated by a cell ID and a slot number/OFDM symbol index within 20ms corresponding to a default periodicity of an SS burst set. And, anindex of an SS block can be determined based on an index of a slot andan index of an OFDM symbol.

Meanwhile, it is necessary to perform scrambling on NR-PBCH DMRS using1008 cell IDs and SS block indexes of 3 bits. This is because, whendetection performances are compared according to the number ofhypotheses of a DMRS sequence, it is known as detection performance of 3bits is most suitable for the number of hypotheses of the DMRS sequence.However, since it is examined as detection performance of 4 to 5 bitshas little performance loss, it is o.k. to use the number of hypothesesof 4 to 5 bits.

Meanwhile, since it is necessary for a DMRS sequence to represent an SSblock time index and 5 ms boundary, it is necessary to design 16hypotheses in total.

In other word, it is necessary for a DMRS sequence to represent a cellID, SS block indexes included in an SS burst set, and a half frameindication. The DMRS sequence can be initialized by the cell ID, the SSblock indexes included in the SS burst set, and the half frameindication. An equation for initializing the DMRS sequence is shown inthe following.

c _(init)=(NS _(ID) ^(SS/PBCHblock)+1+8·HF)·(2·N _(ID) ^(cell)+1)·2¹⁰ +N_(ID) ^(cell)

In this case, N_(ID) ^(SS/PBCHblock) corresponds to SS block indexes inan SS block group, N_(ID) ^(Cell) corresponds to a cell ID, and HEcorresponds to a half frame indication index having a value of {0, 1}.

Similar to an LTE DMRS sequence, NR-PBCH DMRS sequence can be generatedusing a gold sequence of a length of 31 or a gold sequence of a lengthof 7 or 8.

Meanwhile, since detection performance using the gold sequence of alength of 31 is similar to detection performance using the gold sequenceof a length of 7 or 8, the present invention proposes to use the goldsequence of a length of 31 like LTE DMRS does. In a frequency rangeequal to or wider than 6 GHz, it may consider using a gold sequence of alength longer than 31.

A DMRS sequence r_(N) _(ID) _(SS/PBCH block) (m), which is modulatedusing QPSK, can be defined by equation 12 in the following.

$\begin{matrix}{{{r_{N_{ID}^{{SS}/{PBCHblock}}}(m)} = {{\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {2m} )}}} )} + {j\frac{1}{\sqrt{2}}( {1 - {2 \cdot {c( {{2m} + 1} )}}} )}}},\mspace{20mu} {m = 0},1,\ldots,143} & \lbrack {{Equation}\mspace{14mu} 12} \rbrack\end{matrix}$

It may consider BPSK and QPSK as a modulation type for generating a DMRSsequence. Detection performance of the BPSK is similar to detectionperformance of the QPSK. However, since correlation performance of theQPSK is superior to correlation performance of the BPSK, the QPSK ismore suitable for a modulation type for generating the DMRS sequence.

In the following, a method of configuring a PBCH DMRS sequence isexplained in more detail. A PBCH DMRS sequence is configured using agold sequence. Two m-sequences are configured by a polynomial expressionthat configures the same length. If a length of a sequence is short, onem-sequence can be replaced with a short polynomial expression.

Embodiment 3-1

Two m-sequences constructing a gold sequence are configured with thesame length. An initial value of one m-sequence uses a fixed value andan initial value of another m-sequence can be initialized by a cell IDand a time indicator.

For example, a gold sequence of a length of 31 used in LTE can be usedas a gold sequence. A CRS of legacy LTE uses a gold sequence of a lengthof 31 and is initialized based on 504 cell IDs, 7 OFDM symbols, and 140time indicators based on 20 slots to generate a different sequence.

In a frequency band equal to or narrower than 60 GHz, 15 kHz subcarrierspacing and 30 kHz subcarrier spacing are used. Hence, the maximumnumber of SS blocks included in a range of 5 ms corresponds to 8 and themaximum number of SS blocks included in a range of 20 ms corresponds to32. In particular, when information on 5 ms boundary is obtained using aPBCH DMRS sequence in a range of 20 ms, an operation identical to anoperation of searching for 32 SS blocks is performed. In NR, the numberof cell IDs corresponds to 1008. In particular, although the number ofcell IDs is doubled compared to LTE, since the number of SS blocks isless than 70 (=140/2), it may use the aforementioned sequence.

Meanwhile, in a band equal to or wider than 6 GHz, although the maximumnumber of SS blocks corresponds to 64 in a range of 5 ms, the maximumnumber of SS block indexes forwarded via PBCH DMRS corresponds to 8.Since the maximum number of SS block indexes forwarded via PBCH DMRS isidentical to the maximum number of SS block indexes in a band equal toor narrower than 6 GHz, in a band equal to or wider than 6 GHz, it maybe able to generate a sequence according to a cell ID and a timeindicator using a gold sequence of a length of 31.

As a different method, it may apply a gold sequence of a differentlength according to a frequency range. In a band equal to or wider than6 GHz, it may use 120 kHz subcarrier spacing and 240 kHz subcarrierspacing. Hence, the number of slots included in 10 ms is increased asmany as 8 times (80 slots) and 16 times (160 slots) compared to the 15kHz subcarrier spacing. In particular, if a sequence of a data DMRS isinitialized using C-RNTI of 16 bits and a slot index, it may be requiredto have a polynomial expression of a length longer than 31. If alength-N(>31) gold sequence is introduced according to the requirement,the sequence can be used for scrambling a PBCH DMRS and PBCH. In thiscase, it may apply a gold sequence of a different length according to afrequency range. In a band equal to or narrower than 6 GHz, a length-31gold sequence is used. In a band equal to or wider than 6 GHz, alength-N(>31) gold sequence can be used. In this case, an initial valuecan be applied using a method similar to the aforementioned method.

Embodiment 3-2

Two m-sequences constructing a gold sequence are configured with thesame length. An initial value of one m-sequence is initialized using atime indicator and an initial value of another m-sequence can beinitialized using a cell ID or a cell ID and a different time indicator.For example, a length-31 gold sequence used in LTE can be used as a goldsequence. An m-sequence to which a fixed initial value is applied isinitialized using a time indicator. And, another m-sequence isinitialized using a cell ID.

As a different method, if a half radio frame boundary (5 ms), SFN top 1bit (10 ms boundary), and the like are transmitted via PBCH DMRStogether with an SS block index, the half radio frame boundary (5 ms)and the SFN top 1 bit (10 ms boundary) are indicated in a firstm-sequence and the SS block index can be indicated in a secondm-sequence.

As mentioned earlier in the embodiment 1, although a gold sequence of adifferent length is introduced according to a frequency range, it may beable to apply the aforementioned sequence initialization method.

Embodiment 3-3

A gold sequence is configured by an m-sequence having a polynomialexpression of a different length. An m-sequence having a long polynomialexpression is used for information requiring many indications and anm-sequence having a relatively short polynomial expression is used forinformation requiring less indication.

A sequence of PBCH DMRS is generated according to time information suchas a cell ID and an SS block indication. In order to represent 1008 cellIDs and the P number of time information (e.g., SS block indicator 3bits), it may use two polynomial expressions of a different length. Forexample, it may use a polynomial expression of a length of 31 toidentify a cell ID and it may use a polynomial expression of a length of7 to identify time information. In this case, two m-sequences can beinitialized using a cell ID and time information, respectively.Meanwhile, in the aforementioned example, the length-31 polynomialexpression may correspond to a part of the m-sequence constructing thegold sequence used in LTE and the length-7 polynomial expression maycorrespond to one of two m-sequences defined for configuring NR-PSSsequence or NR-SSS sequence.

Embodiment 3-4

One sequence is generated from an M-sequence having a short polynomialexpression and another sequence is generated from a gold sequenceconfigured by M-sequences having a long polynomial expression. The twosequences are multiplied by an element wise.

In the following, a method of configuring an initial value of a sequenceused as a PBCH DMRS sequence is explained. The PBCH DMRS sequence isinitialized by a cell ID and a time indicator. And, when a bit stringused for the initialization is represented as c(i)*2{circumflex over( )}i, i=0, . . . ,30, c(0)˜c(9) are determined by a cell ID andc(10)˜c(30) are determined by a cell ID and a time indicator. Inparticular, a part of information of the time indicator can be forwardedto a bit corresponding to c(10)˜c(30). An initialization method may varyaccording to the attribute of the information.

Embodiment 4-1

When initialization is performed using a cell ID and an SS block index,as mentioned in the foregoing description, c(0)˜c(9) are determined bythe cell ID and c(10)˜c(30) are determined by the cell ID and the SSblock index. In equation 13 in the following, NID corresponds to thecell ID and SSBID corresponds to the SS block index.

2{circumflex over ( )}10*(SSBID*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1)*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1)*(2*NID+1))+NID  [Equation 13]

Embodiment 4-2

In the initialization method described in the embodiment 4-1, if a timeindicator is added, an initialization value is configured in a form ofincreasing SS blocks. In a range of 5 ms, when the number of SS blockindexes forwarded via a PBCH DMRS sequence corresponds to P, if it isattempted to find out a half radio frame boundary in a DMRS sequence, itcan be represented by an effect that the number of SS block indexes isdoubled. If it is attempted to find out not only the half frame boundarybut also 10 ms boundary, it can be represented by an effect that thenumber of SS block indexes is increased four times. An equation for theembodiment 4-2 is shown in the following.

2{circumflex over ( )}10*((SSBID+P*(i))*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1+P*(i))*(2*NID+1))+NID+1

2{circumflex over ( )}10*((SSBID+1+P*(i))*(2*NID+1))+NID  [Equation 14]

In this case, if 0, 5, 10, 15 ms boundaries are represented, icorresponds to 0, 1, 2, and 3. If a half frame boundary is representedonly, i corresponds to 0 and 1.

Embodiment 4-3

In the initialization method described in the embodiment 2-1, if a timeindicator is added, the time indicator can be indicated in a manner ofbeing separated from an SS block index. For example, c(0)˜c(9) aredetermined by a cell ID, c(10)˜c(13) are determined by an SS blockindex, and c(14)˜c(30) can be determined by the added time indicatorsuch as a half frame boundary, SFN information, and the like. Anequation for the embodiment 2-3 is shown in the following.

2{circumflex over ( )}13*(i)+2{circumflex over ( )}10*((SSBID+1))+NID

2{circumflex over ( )}13*(i+1)+2{circumflex over ( )}10*((SSBID+1))+NID

2{circumflex over ( )}13*(i)+2{circumflex over ( )}10*((SSBID+1))+NID+1

2{circumflex over ( )}13*(i+1)+2{circumflex over( )}10*((SSBID+1))+NID+1  [Equation 15]

Embodiment 4-4

The maximum number (i.e., L) of SS blocks is determined according to afrequency range. In this case, when the number of SS block indexesforwarded via a PBCH DMRS sequence corresponds to P, if the L is equalto or less than P, all of the SS block indexes are forwarded via a DMRSsequence and the SS block indexes are identical to indexes obtained fromthe DMRS sequence. Meanwhile, if the L is greater than the P, the SSblock indexes are configured by a combination of indexes forwarded viathe DMRS sequence and indexes forwarded via PBCH contents.

When the indexes used by the DMRS sequence correspond to SSBID and theindexes included in the PBCH contents correspond to SSBGID, it mayconsider 3 cases described in the following.

(1) Case 0: L<=P

SS-PBCH block index=SSBID

(2) Case 1: L>P

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Floor (SS-PBCH block index/P)

SSBGID=Mod(SS-PBCH block index, P)

(3) Case 2: L>P

SS-PBCH block index=SSBID*P+SSBGID

SSBID=Mod(SS-PBCH block index, P)

SSBGID=Floor (SS-PBCH block index/P)

Meanwhile, a pseudo-random sequence for generating NR-PBCH DMRS sequenceis defined by a gold sequence of a length of 31 and a sequence of alength of M_(PN) is defined by equation 16 described in the following.

c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2

x ₁(n+31)=(x ₁(n+3)+x(n))mod 2

x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  [Equation 16]

In this case, n=0, 1, . . . , M_(PN)−1 and N_(C)=1600 are satisfied. Afirst m-sequence has an initial value of x_(i)(0)=1, x₁(n)=0, n=1, 2, .. . , 30 and an initial value of a second m-sequence is defined byc_(init)=Σ_(i=0) ³⁰(i)·2^(i). In this case,

${{x_{2}(i)} = {\lfloor \frac{c_{init}}{2^{i}} \rfloor {mod}\; 2}},{i = 0},1,\Lambda,30$

is satisfied.

19. NR-PBCH DMRS Pattern Design

In relation to a frequency position of a DMRS, it may consider two typesof DMRS RE mapping method. According to a fixed RE mapping method, an RSmapping region is fixed in frequency domain. According to a variable REmapping method, an RS position is shifted according to a cell ID using aVshift method. Since the variable RE mapping method randomizesinterference, it may have a merit in that it is able to obtain anadditional performance gain. Hence, it is preferable to use the variableRE mapping method.

The variable RE mapping method is explained in more detail. A complexmodulation symbol a_(k,l) included in a half frame can be determined byequation 17 in the following.

$\begin{matrix}{{a_{k,l} = {r_{N_{ID}^{{SS}/{PBCHblock}}}( {{72 \cdot l^{\prime}} + m^{\prime}} )}}{k = {{{4m^{\prime}} + {v_{shift}\mspace{20mu} {if}\mspace{14mu} l}} \in \{ {1,3} \}}}{l = \{ {{{\begin{matrix}1 & {l^{\prime} = 0} \\3 & {l^{\prime} = 1}\end{matrix}m^{\prime}} = 0},1,\ldots \mspace{14mu},{{71v_{shift}} = {N_{ID}^{cell}{mod}\; 3}}} }} & \lbrack {{Equation}\mspace{14mu} 17} \rbrack\end{matrix}$

In this case, k and l correspond to a subcarrier positioned in an SSblock and an OFDM symbol index, respectively. r_(N) _(ID)_(SS/PBCH block) (m) corresponds to a DMRS sequence. Meanwhile, thecomplex modulation symbol can also be determined by v_(shift)=N_(ID)^(cell) mod 4.

And, it may consider RS power boosting for performance enhancement. Ifthe RS power boosting and Vshift are used together, it may be able toreduce interference from interference TRP (total radiated power). And,when a detection performance gain of the RS power boosting isconsidered, −1.25 dB is preferable for a ratio of PDSCH EPRE to RS EPRE.

Meanwhile, in order to design a DMRS, it is necessary to determine DMRSoverhead, a time/frequency position, and a scrambling sequence. OverallPBCH decoding performance can be determined by channel estimationperformance and NR-PBCH coding rate. The number of REs for transmittinga DMRS has a trade-off relation between the channel estimationperformance and the PBCH coding rate, it is necessary to determine thenumber of REs appropriate for a DMRS.

According to an experiment result, it is able to see that it may havebetter performance when 4 REs (⅓ density) per RB are allocated to aDMRS. When 2 OFDM symbols are allocated to transmit NR-PBCH, 192 REs areused for a DMRS and 384 REs are used for MIB transmission. In this case,if a payload size corresponds to 64 bits, it may obtain 1/12 codingspeed identical to coding speed of LTE PBCH.

A DMRS can be used for a phase reference of NR-PBCH. In this case, inorder to map the DMRS, it may consider two methods. One is an equalinterval mapping method. Each of PBCH symbols is used and a DMRSsequence is mapped to a subcarrier according to the same interval.

In case of mapping a DMRS with a non-equal interval, a DMRS sequence isnot mapped within NR-SSS transmission bandwidth while each of PBCHsymbols is used. Instead, NR-SSS is used for PBCH demodulation. Hence,when a DMRS is mapped with a non-equal interval, it may be necessary tohave more resources in estimating a channel and more REs can be used totransmit data compared to the equal interval mapping method. And, sincea residual CFO may exist in an initial access procedure, channelestimation using an SSS symbol may not be accurate. In particular, theequal interval mapping method has a merit in estimating CFO and trackingprecise time.

And, if SS block time indicator is forwarded via a PBCH DMRS, the equalinterval mapping method may have an additional advantage. When PBCHdecoding performance according to RE mapping method is evaluated, it isable to see that the equal interval mapping method has betterperformance compared to the non-equal interval mapping method. Inparticular, when an initial access procedure is performed, the equalinterval mapping method is more appropriate for performing the initialaccess procedure. And, in relation to a frequency position of a DMRS, itmay assume DMRS mapping interleaved in frequency domain capable of beingshifted according to a cell ID. When DMRS patterns are mapped with thesame interval, in case of 1-D channel estimation, it is preferable touse DFT-based channel estimation that provides optimized performance.

In the following, an embodiment for an RE mapping method of a PBCH DMRSsequence is explained.

Embodiment 5-1

A sequence length for a DMRS is determined by the number of REs used asa PBCH DMRS and a modulation order.

If the M number of REs is used for a PBCH DMRS and BPSK modulation isperformed on a sequence, it may be able to generate a sequence of alength of M. The BPSK modulation is performed according to an order ofthe sequence and a modulated symbol is mapped to a DMRS RE. For example,if two OFDM symbols include 144 PBCH DMRS REs in total, a sequence of alength of 144 is generated using a single initial value, BPSK modulationis performed, and RE mapping is performed.

Meanwhile, if the M number of REs is used for a PBCH DMRS and QPSKmodulation is performed on a sequence, it may be able to generate asequence of a length of 2*M. If a sequence string corresponds to s(0), .. . , s(2*M−1), QPSK modulation is performed by combining a sequence ofan even-numbered index with a sequence of an odd-numbered index. Forexample, if two OFDM symbols include 144 PBCH DMRS REs in total, asequence of a length of 288 is generated using a single initial value,QPSK modulation is performed, and a modulated sequence of a length of144 is mapped to a DMRS RE.

And, if the N number of REs is used for a PBCH DMRS in an OFDM symboland BPSK modulation is performed on a sequence, it may be able togenerate a sequence of a length N. The BPSK modulation is performedaccording to an order of the sequence and a modulated symbol is mappedto a DMRS RE. For example, if one OFDM symbol includes 72 PBCH DMRS REsin total, a sequence of a length of 72 is generated using a singleinitial value, BPSK modulation is performed, and RE mapping isperformed. If one or more OFDM symbols are used for PBCH transmission,it may be able to generate a different sequence by performinginitialization according to each of the OFDM symbols. Or, it may be ableto identically map a sequence generated in a previous symbol.

And, if the N number of REs is used for a PBCH DMRS in an OFDM symboland QPSK modulation is performed on a sequence, it may be able togenerate a sequence of a length of 2*N. If a sequence string correspondsto s(0), . . . , s(2*M−1), QPSK modulation is performed by combining asequence of an even-numbered index with a sequence of an odd-numberedindex. A modulated symbol is mapped to a DMRS RE. For example, if oneOFDM symbol includes 72 PBCH DMRS REs in total, a sequence of a lengthof 144 is generated using a single initial value, QPSK modulation isperformed, and RE mapping is performed. If one or more OFDM symbols areused for PBCH transmission, it may be able to generate a differentsequence by performing initialization according to each of the OFDMsymbols. Or, it may be able to identically map a sequence generated in aprevious symbol.

Embodiment 5-2

When the same sequence is mapped to a different symbol, it may apply acyclic shift. For example, when two OFDM symbols are used, if amodulated sequence string of a first OFDM symbol is sequentially mappedto RE, RE mapping is performed by cyclic shifting a modulated sequencestring as much as an offset corresponding to ½ of a modulated sequencestring N in a second OFDM symbol. When NR-PBCH uses 24 RBs and NR-SSSuses 12 RBs, if the NR-SSS and the NR-PBCH match a center frequency RE,the NR-SSS is arranged to RBs ranging from 7^(th)RB to 18^(th) RB. Itmay be able to estimate a channel rom the NR-SSS. When an SS block indexis detected from NR-PBCH DMRS, it may attempt to perform coherentdetection using an estimated channel. If the cyclic shift method is usedto easily perform the detection, it may be able to obtain an effect thata sequence string of PBCH DMRS is transmitted over two OFDM symbols atthe center 12 RBs in which the NR-SSS is transmitted.

Embodiment 5-3

When a time indication rather than an SS block indication istransmitted, a cyclic shift value can be determined according to thetime indication.

When the same sequence is mapped to OFDM symbols, the same cyclic shiftcan be applied to each of the OFDM symbols or a different cyclic shiftcan be applied to each of the OFDM symbols. If a sequence is generatedin accordance with the total number of DMRS REs included in an OFDMsymbol used as PBCH, a cyclic shift is applied to the entire sequencesand the sequences are mapped to a DMRS RE. As a different example of thecyclic shift, it may consider reverse mapping. For example, when amodulated sequence string corresponds to s(0), . . . , s(M−1), reversemapping may correspond to s(M−1), . . . , s(0).

In the following, a frequency position of a PBCH DMRS RE is explained.

A frequency position of an RE used for a PBCH DMRS can be changed by aspecific parameter.

Embodiment 6-1

When a DMRS is arranged in every N (e.g., N=4) number of REs, a maximumrange capable of shifting an RE position in a frequency axis can beconfigured by N. For example, it may be able to represent the maximumrange as N*m+v_shift (where, m=0, . . . , 12×NRB_PBCH−1, v_shift=0, . .. , N−1).

Embodiment 6-2

An offset of shifting shifted on a frequency axis can be determined by acell ID. The offset of the shifting can be determined using a cell IDobtained from a PSS and an SSS. In NR system, a cell ID can beconfigured by a combination of a cell_ID(1) obtained from a PSS and acell_ID(2) obtained from an SSS. In this case, the cell ID can berepresented as Cell_ID(2)*3+Cell_ID(1). In particular, the offset of theshifting can be determined by information on the obtained cell ID orpartial information of the cell ID information. For example, the offsetcan be calculated using an equation described in the following.

v_shift=Cell-ID mod N (where, N is a frequency interval of DMRS, forexample, N is configured by 4)

v_shift=Cell-ID mod 3 (interference randomization effect among 3adjacent cells, DMRS frequency interval may be greater than 3, forexample, N is configured by 4)

v_shift=Cell_ID(1)(Cell_ID(1) obtained from PSS is used as an offsetvalue of shift)  [Equation 18]

Embodiment 6-3

An offset of shifting shifted on a frequency axis can be determined by apartial value of time information. For example, the offset of the shiftcan be determined by a half radio frame boundary (5 ms) or top 1-bitinformation (10 ms) of SFN. For example, the offset can be calculatedusing an equation described in the following.

v_shift=0,1,2,3(DMRS position is shifted in every 0/5/10/15 ms. Iffrequency interval of DMRS corresponds to 4, there are 4 shiftopportunities.)

v_shift=0,1(Shift is performed according to 0/5 ms boundary or 0/10 msboundary)

v_shift=0,2(Shift is performed according to 0/5 ms boundary or 0/10 msboundary. If frequency interval of DMRS corresponds to 4, shift isperformed as much as 2 corresponding to maximum interval.)  [Equation19]

Embodiment 6-4

An offset of shifting shifted on a frequency axis can be determined by acell ID and a partial value of time information. In particular, theoffset can be configured by a combination of the embodiment 2-3 and theembodiment 2-3. In particular, the offset is configured by a combinationof vshift_cell corresponding to shift according to a cell ID andvshift_frame corresponding to shift according to time information. Theinterval can be represented by modulo of DMRS RE interval N. The offsetcan be calculated using an equation described in the following.

vshift=(vshift_cell+vshift_frame)mod N  [Equation 20]

FIG. 27 is a diagram illustrating an example of mapping a DMRS in an SSblock.

In the following, a power ratio of PBCH DMRS RE to data RE is explained.An RE for transmitting PBCH DMRS can be transmitted using power higherthan power used for transmitting RE for transmitting data of OFDM symbolin which the PBCH DMRS is included.

Embodiment 7-1

A ratio of energy per data RE to energy per DMRS RE uses a fixed valueaccording to a frequency band. In this case, a fixed value can be usedin all frequency bands or a specific power ratio can be applied in aspecific frequency band. In particular, it may apply a different powerratio according to a frequency band. For example, in a band equal tonarrower than 6 GHz where ICI is dominantly acts, high power is used. Ina band equal to wider than 6 GHz where noise is limited, the same powercan be used.

For clarity, a power ratio is represented by ‘a ratio of energy per dataRE to energy per DMRS RE’ in the present invention. However, the powerratio can be represented in various ways. For example, the power ratiocan be represented as follows.

-   -   Ratio of power per DMRS RE to power per data RE    -   Ratio of energy per DMRS RE to energy per data RE    -   Ratio of power per data RE to power per DMRS RE    -   Ratio of energy per data RE to energy per DMRS RE

Embodiment 7-2

Power of an RE used as a DMRS can be configured by a value lower than 3dB compared to power of an RE used as data. For example, when 3 REs areused as DMRS and 9 REs are used as data among 12 REs and when 4 REs areused as DMRS and 8 REs are used as data among 12 REs, assume that PBCHdecoding performance is similar. In this case, in order to obtain asimilar effect by using 3 REs instead of 4 REs, power of 3 RE DMRS isincreased about 1.3334 times according to an RE and power of adjacentdata REs is adjusted to 0.8889 times. By doing so, it is able toincrease power of DMRS while the entire power of OFDM symbol ismaintained. In this case, a power boosting level becomes about 1.76 dB(=10*log(1.3334/0.8889)).

As a different example, if performance similar to detection performanceof 4.8 RE DMRS is provided by using 3 REs/9 REs (DMRS/data), a powerboosting level becomes about 3 dB (about 2 dB in case of 4.15 RE DMRS).

Embodiment 7-3

When NR system operates as Non Stand Alone (NSA) in a manner of beingassociated with LTE system, it may be able to indicate a ratio of energyper data RE to energy per DMRS RE.

20. NR-PBCH TTI Boundary Indication

NR-PBCH TTI corresponds to 80 ms and a default periodicity of an SSburst set corresponds to 20 ms. This indicates that NR-PBCH istransmitted 4 times within the NR-PBCH TTI. When the NR-PBCH is repeatedwithin the NR-PBCH TTI, it is necessary to indicate a boundary of theNR-PBCH TTI. For example, similar to LTE PBCH, the NR-PBCH TTI boundarycan be indicated by a scrambling sequence of the NR-PBCH.

Referring to FIG. 28, the scrambling sequence of the NR-PBCH can bedetermined by a cell ID and TTI boundary indication. A periodicity of anSS burst set may have a plurality of values. Hence, the number ofindexes for the TTI boundary indication can be changed according to theperiodicity of the SS burst set. For example, 4 indexes are necessaryfor a default periodicity (i.e., 20 ms) and 16 indexes are necessary fora shorter periodicity (i.e., 5 ms).

Meanwhile, NR system supports both single beam transmission andmulti-beam transmission. When a plurality of SS blocks are transmittedwithin the periodicity of the SS burst set, an SS block index can beassigned to each of a plurality of the SS blocks. In order to performrandomization between SS blocks for inter-cell, it is necessary todetermine a scrambling sequence by an index related to an SS block. Forexample, If an index of an SS block is derived from an index of a slotand an index of an OFDM symbol, a scrambling sequence of NR-PBCH can bedetermined by the index of the sot and the index of the OFDM symbol.

And, if a network sets such a short period as 5 ms or 10 ms to an SSburst set, the SS burst set can be more transmitted during the sametime. In this case, a UE may have ambiguity regarding a TTI boundary ofNR-PBCHs transmitted within the default periodicity. In order toindicate an NR-PBCH TTI boundary for a periodicity shorter than thedefault periodicity, it may consider a different scrambling sequence ofNR-PBCH for the periodicity shorter than the default periodicity. Forexample, if a periodicity of 5 ms of an SS burst set is assumed, 16scrambling sequences are applied to NR-PBCH. By doing so, it may have amerit in that it is able to indicate a precise boundary of NR-PBCHtransmission within NR-PBCH TTI. On the contrary, blind detectioncomplexity for NR-PBCH decoding is increased. In order to reduce theblind decoding complexity of the NR-PBCH, it may consider applying adifferent NR-SSS sequence to distinguish NR-SSS having a defaultperiodicity from NR-SSS additionally transmitted within the defaultperiodicity.

21. Time Index Indication Method

Referring to FIG. 29, time information includes SFN (system framenumber), a half frame interval, and an SS block time index. The timeinformation can be represented by 10 bits for the SFN, 1 bit for thehalf frame, and 6 bits for the SS block time index. In this case, a partof the 10 bits for the SFN can be included in PBCH contents. And,NR-DMRS can include 3 bits among the 6 bits for the SS block time index.

In FIG. 29, embodiments for the time index indication method aredescribed in the following.

-   -   Method 1: S2 S1 (PBCH scrambling)+S0 C0 (PBCH contents)    -   Method 2: S2 S1 S0 (PBCH scrambling)+C0 (PBCH contents)    -   Method 3: S2 S1 (PBCH scrambling)+S0 C0 (PBCH DMRS)    -   Method 4: S2 S1 S0 (PBCH scrambling)+C0 (PBCH DMRS)

If half frame indication is forwarded via the NR-PBCH DMRS, it may beable to have additional performance enhancement by combining PBCH datain every 5 ms. To this end, as shown in the methods 3 and 4, 1 bit forthe half frame indication can be forwarded via the NR-PBCH DMRS.

When the methods 3 and 4 are compared, although the method 3 reduces adecoding count, the method 3 may bring about a loss of PBCH DMRSperformance. If PBCH DMRS is able to forward 5 bits including S0, C0,B0, B1, and B2 with excellent performance, the method 3 can be used asan appropriate timing indication method. However, if the PBCH DMRS isunable to forward the 5 bits with excellent performance, the method 4can be used as an appropriate timing indication method.

In particular, the top 7 bits of the SFN can be included in the PBCHcontents and the bottom 2 or 3 bits can be forwarded via PBCHscrambling. And, the bottom 3 bits of the SS block index are included inthe PBCH DMRS and the top 3 bits of the SS block index can be includedin the PBCH contents.

In addition, it may consider a method of obtaining an SS block timeindex of a neighboring cell. Since decoding via a DMRS sequence showsbetter performance compared to decoding via the PBCH contents, if a DMRSsequence is changed within 5 ms, it is able to transmit 3 bits of the SSblock index.

Meanwhile, in a frequency range equal to or narrower than 6 GHz, an SSblock time index can be transmitted using NR-PBCH DMRS of a neighboringcell only. On the contrary, in a frequency range equal to or wider than6 GHz, since 64 SS block indexes are separately indicated via PBCH-DMRSand PBCH contents, it is not necessary for a UE to perform decoding onPBCH of a neighboring cell.

However, if decoding is performed on PBCH-DMRS and PBCH contentstogether, it may bring about additional NR-PBCH decoding complexity anddecoding performance of PBCH can be deteriorated compared to a case ofusing the PBCH-DMRS only. As a result, it may be difficult to performdecoding on PBCH to receive an SS block of a neighboring cell.

It may consider a method for a serving cell to provide a UE with aconfiguration related to an SS block index of a neighboring cell insteadof a method of decoding PBCH of the neighboring cell. For example, theserving cell provides the UE with a configuration related to the top 3bits of an SS block index of a target neighboring cell and the UEdetects the bottom 3 bits via PBCH-DMRS. Then, the UE is able to obtainthe SS block index of the target neighboring cell by combining the top 3bits with the bottom 3 bits.

22. Soft Combining

It is necessary for NR system to support wise soft combining to an SSburst set for efficient resource utilization and PBCH coverage. SinceNR-PBCH is updated in every 80 ms and the SS bust set is transmitted inevery default periodicity of 20 ms, soft combining of at least 4 timescan be performed on NR-PBCH decoding. If a periodicity shorter than thedefault periodicity is indicated to the SS burst set, more OFDM symbolscan be used for soft combining for PBCH.

23. PBCH Decoding for the Neighboring Cell Measurements

In order to measure a neighboring cell, it is necessary to determinewhether or not a UE performs decoding on NR-PBCHs of neighboring cells.Since decoding of neighboring cells increases UE complexity, it ispreferable not to increase unnecessary complexity. Hence, it isnecessary for the UE to assume that the UE needs not decode NR-PBCH of aneighboring cell when the UE measures the neighboring cell.

On the contrary, if an SS block index is forwarded via a signal of aspecific type, the UE performs signal detection and may be then able toobtain SS block indexes of neighboring cells. By doing so, it is able toreduce UE complexity. Meanwhile, the signal of the specific type maycorrespond to NR-PBCH DMRS.

24. Measurement Result Evaluation

In the following, a performance measurement result according to apayload size, a transmission scheme, and a DMRS is explained. In thiscase, assume that two OFDM symbols having 24 RBs are used to transmitNR-PBCH. And, assume that an SS burst set (i.e., 10, 20, 40, 80 ms) hasa plurality of periods and a coded bit is transmitted within 80 ms.

(1) Payload Size and NR-PBCH Resource

FIG. 30 provides an evaluation result according to MIB payload size(e.g., 64, 80 bits). In this case, assume that 389 REs and 192 REs for aDMRS are used in two OFDM symbols and 24 RBs. And, assume that a singleantenna port-based transmission scheme (i.e., TD-PVS) is used.

Referring to FIG. 30, NR-PBCH of a period of 20 ms shows an error rateof 1% in −6 dB SNR. In case of a payload of 64 bits, it is able to seethat the payload has a gain as much as 0.8 dB compared to a payload of80 bits. In particular, if a payload size between 64 bits and 80 bits isassumed, a performance requirement of NRR-PBCH (i.e., 1% BLER in −6 dBSNR) can be satisfied using 24 RBs and 2 OFDM symbols.

(2) Transmission Scheme

FIG. 31 provides an evaluation result according to NR-PBCH transmissionscheme such as TD-PVS and FD-PVS. A precoder is cycled in every PBCHtransmission subframe (e.g., 20 ms) for the TD-PVS and all of the Nnumber of RBs (e.g., N corresponds to 6) for the FD-PVS. In FIG. 31,soft combining of NR-PBCH is assumed in a plurality of periods (i.e.,10, 20, 40, and 80 ms) of an SS burst set.

As shown in FIG. 31, a TD-PVS (time-domain precoding vector switching)scheme shows excellent channel estimation performance better thanperformance of an FD-PVS (frequency-domain precoding vector switching).In this case, it is able to see that channel estimation performance ismore important than transmit diversity gain in a very low SNR region.

(3) DMRS Density

In a low SNR region, channel estimation performance enhancement is animportant element for enhancing demodulation performance. However, if RSdensity of NR-PBCH increases, although the channel estimationperformance is enhanced, coding speed is reduced. In order to compromisebetween the channel estimation performance and a channel coding gain,decoding performance is compared according to DMRS density. FIG. 32illustrates DMRS density.

FIG. 32 (a) illustrates a case of using 2 REs per symbol for a DMRS,FIG. 32 (b) illustrates a case of using 4 REs per symbol for a DMRS, andFIG. 32 (c) illustrates a case of using 6 REs per symbol for a DMRS.And, assume that the present evaluation uses a single port-basedtransmission scheme (i.e., TD-PVS).

FIG. 32 illustrates an embodiment of a DMRS pattern for a single antennaport-based transmission. Referring to FIG. 32, while a DMRS positionmaintains the same distance between reference signals in frequencydomain, RS density is changed. FIGS. 33 and 34 illustrate a performanceresult of a DMRS according to reference signal density.

As shown in FIGS. 33 and 34, NR-PBCH decoding performance shown in FIG.32 (b) shows excellent channel estimation performance. In particular,the NR-PBCH decoding performance is superior to the performance shown inFIG. 32 (a). On the contrary, referring to FIG. 32 (c), since an effectof a coding speed loss is greater than a gain of channel estimationperformance enhancement, performance shown in FIG. 32 (c) is inferior tothe performance of FIG. 32 (b). Due to the abovementioned reason, it ispreferable to design RS density of 4 REs per symbol.

(4) DMRS Time Position and CFO Estimation

If NR system supports self-contained DMRS, it may be able to performfine frequency offset tracking on NR-PBCH using the self-contained DMRS.Since frequency offset estimation accuracy depends on an OFDM symboldistance, as shown in FIG. 35, it may assume three types of NR-PBCHsymbol spacing.

CFO estimation is performed in SNR of −6 dB according to each of NR-PBCHsymbol spacing shown in FIG. 35. A sample of 10% CFO (1.5 kHz) isapplied in a subframe. 4 REs per symbol are used as an independent RSand the REs are included in a symbol in which PBCH is transmitted.

FIGS. 36 and 37 illustrate CDF of CFO estimated according to a differentNR-PBCH symbol spacing. As shown in FIGS. 36 and 37, 90% of UEs canestimate CFO of 1.5 kHz within an error range of ±200 Hz. If minimum 2symbols are introduced as NR-PBCH symbol spacing, 95% of UEs canestimate CFO within an error range of ±200 Hz and 90% of UEs canestimate CFO within an error range of ±100 Hz.

A phase offset due to CFO increases as spacing is getting bigger. If aninterval between PBCH symbols is bigger, CFO estimation performance isbetter. Hence, similar to noise suppression, it is able to easilymeasure the phase offset. And, if a size of an average window is big, itis able to increase accuracy of CFO estimation.

In the following, detection performance of an SS block index accordingto the number of DMRS sequence hypotheses, a modulation type, sequencegeneration, and DMRS RE mapping is explained. In the present measurementresult, assume that 2 OFDM symbols are used for transmitting NR-PBCH to24 RBs. And, it may consider multiple periods of an SS burst set. Themultiple periods may include 10 ms, 20 ms, and 40 ms.

(5) Number of DMRS Hypotheses

FIG. 38 illustrates a measurement result according to an SS block index.In this case, 144 REs are used for a DMRS within 24 RBs and 2 OFDMsymbols 432 REs are used for information. And, assume that a longsequence (e.g., a gold sequence of a length of 31) is used as a DMRSsequence and QPSK is used.

Referring to FIG. 38, if detection performance of 3 to 5 bits ismeasured two times by accumulating the detection performance, it showsan error rate of 1% in SNR of −6 dB. In particular, information of 3 to5 bits can be used as the number of hypotheses for a DMRS sequence inthe aspect of detection performance.

(6) Modulation Type

FIGS. 39 and 40 illustrate performance measurement results of BPSK andQPSK. The present experiment is performed based on an assumption that aDMRS hypothesis corresponds to 3 bits and a long sequence is used as aDMRS sequence. A power level of interference TRP is identical to a powerlevel of serving TRP.

Referring to FIGS. 39 and 40, performance of BPSK is similar toperformance of QPSK. In particular, there is no significant differencein terms of performance measurement irrespective of a modulation typefor a DMRS sequence. However, referring to FIGS. 41 and 42, it is ableto see that a correlation property varies depending on BPSK and QPSK.

Referring to FIGS. 41 and 42, BPSK is more distributed to a region ofwhich correlation amplitude is 0.1 compared to QPSK. Hence, whenmulti-cell environment is considered, it is preferable to use the QPSKas a modulation type of a DMRS. In particular, the QPSK corresponds to amodulation type more suitable for a DMRS sequence in the aspect of thecorrelation property.

(7) Sequence Generation of PBCH DMRS

FIGS. 43 to 44 illustrate a measurement result according to DMRSsequence generation. A DMRS sequence can be generated based on a longsequence of a polynomial expression order equal to or greater than 30 ora short sequence of a polynomial expression order equal to or less than8. And, assume that a hypothesis for a DMRS corresponds to 3 bits and apower level of interference TRP is identical to that of serving TRP.

Referring to FIGS. 43 to 44, it is able to see that detectionperformance generated based on a short sequence is similar to detectionperformance generated based on a long sequence.

Specifically, although a polynomial expression of a length of 7 isintroduced to a first m-sequence to increase correlation performance ofa sequence, it has no difference with a scheme of using a polynomialexpression of a length of 31 corresponding to a legacy first m-sequence.And, although a sequence is generated by configuring an initial value ofa first m-sequence using SSBID, it has no difference with a scheme offixing an initial value of a legacy first m-sequence and usingSSBID-CellID for a second m-sequence.

Hence, similar to LTE, a length-31 gold sequence is used, an initialvalue of a first m-sequence is fixed for initialization, andSSBID-CellID is used for a second m-sequence.

(8) DMRS RE Mapping

FIGS. 45, 46, and 47 illustrate performance measurement resultsaccording to an equal interval RE mapping method and an unequal intervalRE mapping method. In this case, assume that a hypothesis for a DMRScorresponds to 3 bits, a DMRS sequence is based on a long sequence, anda power level of interference TRP is identical to that of serving TRP.And, assume that there is only one interference source.

NR-SSS is mapped to 144 REs (i.e., 12 RBs) and NR-PBCH is mapped to 288REs (i.e., 24 RBs). Meanwhile, in case of unequal mapping method, assumethat NR-SSS is used for PBCH demodulation and PBCH DMRS is not mappedwithin NR-SSS transmission bandwidth. And, assume that a residual CFOexists.

In particular, the abovementioned contents can be summarized as follows.

(equal interval DMRS mapping) 96 REs per PBCH symbol are used. Inparticular, 192 REs are used in total.

(Unequal interval DMRS mapping) A DMRS sequence is mapped to asubcarrier rather than NR-SSS transmission bandwidth. In this case,NR-SSS is used for PBCH demodulation. 48 REs per PBCH symbol and 128 REsper NR-SSS symbol are used. In particular, 224 REs are used in total.

As shown in FIG. 46, the unequal interval mapping method without CFOincludes more REs for channel estimation. In particular, the unequalinterval mapping method shows performance superior to performance of theequal interval mapping method. However, if a residual CFO of 10% exists,performance of the unequal interval mapping method is degraded. On thecontrary, the equal interval mapping method shows similar performanceirrespective of the CFO. Although the unequal interval mapping methodhas more RE resources for channel estimation, channel estimationaccuracy of NR-SSS symbol is degraded due to the residual CFO. Inparticular, if there is a residual CFO, channel estimation performanceof the equal interval mapping method is superior to the channelestimation performance of the unequal interval mapping method.

As shown in FIG. 47, if variable RE mapping is used, it may have aneffect that interference is randomly distributed. In particular,detection performance of the variable RE mapping is superior toperformance of fixed RE mapping.

FIG. 48 illustrates a measurement result when RS power boost is used. Inthis case, assume that RE transmit power for DMRS is higher than REtransmit power for PBCH data as much as about 1.76 dB(=10*log(1.334/0.889)). If variable RE mapping and DMRS power boostingare used together, interference of a different cell is reduced. As shownin FIG. 48, if RS power boosting is applied, it may have a performancegain as much as 2˜3 dB compared to a case of not applying the RS powerboosting.

On the contrary, the RS power boosting may decrease RE transmit powerfor PBCH data. Hence, the RS power boosting may influence on PBCHperformance. FIGS. 49 to 50 illustrate measurement results for PBCHperformance when RS power boosting is applied and the RS power boostingis not applied. In this case, assume that a periodicity of an SS burstset corresponds to 40 ms and a coded bit is transmitted within 80 ms.

If transmit power of an RE for PBCH data is decreased, performance lossmay occur. However, channel estimation performance is enhanced due tothe increase of RS power, thereby enhancing demodulation performance. Inparticular, as shown in FIGS. 49 to 50, performance is similar in bothcases. In particular, the performance loss due to the decrease of thetransmit power of the RE for PBCH data can be complemented by a gain ofthe channel estimation performance.

Meanwhile, Vshift can be applied to the RS power boosting. In this case,an experiment examination result is explained with reference to FIGS. 51to 52. The Vshift changes a frequency axis position of a DMRS REaccording to a cell ID. When the Vshift is introduced, if a PBCH DMRStransmitted in multi-cell environment is received during two periods andtwo PBCHs are combined with each other, it may have an effect ofenhancing detection performance due to ICI randomization. If the Vshiftis applied, the detection performance can be considerably increased.

Table 6 in the following shows assumption values of parameters used forthe performance measurement.

TABLE 6 Parameter Value Carrier Frequency 4 GHz Channel Model CDL_C(delay scaling values: 100 ns) Subcarrier Spacing 15 kHz AntennaConfiguration TRP: (1, 1, 2) with Omni- directional antenna element UE:(1, 1, 2) with Omni- directional antenna element Frequency Offset 0% and10% of subcarrier spacing Default period 20 ms Subframe duration  1 msOFDM symbols in SF 14 Number of interfering TRPs 1 Operating SNR −6 dB

(9) SS Block Index Indication

An evaluation result for comparing performance of SS block time indexindication is explained with reference to FIGS. 53 to 56. To this end,it may consider a method of indicating the SS block time indexindication via a PBCH DMRS sequence and a method of indicating the SSblock time index indication via PBCH contents. Assume that indicationindicating an SS block time index and 5 ms slot boundary corresponds to16 states in total (i.e., 4 bits). In the present evaluation, assumethat a single SS block included in an SS burst set is transmitted andtime domain precoder cycling is applied within PBCH TTI. And, assumethat 192 REs are used for a PBCH DMRS and 64 MIB bits including a CRCare applied.

The number of hypotheses for the present evaluation corresponds to 16.This is because 4 bits are required to represent 8 states for an SSblock index and a state for 5 ms boundary in PBCH DMRS. As shown inFIGS. 53 to 54, when an SS block time index is detected using a PBCHDMRS, if accumulation is performed two times, it may be able to achievedetection performance of 0.2% in SNR of −6 dB. According to theexamination result of the present evaluation, it is preferable to use aPBCH DMRS to indicate an SS block index and 5 ms boundary.

On the contrary, as shown in FIGS. 55 and 56, although accumulationdecoding is performed two times, PBCH FER is unable to achieve 1% in SNR−6 dB. Hence, if an SS block time index is defined in PBCH contentsonly, it may be difficult to sufficiently secure detection performanceof the SS block time index.

Table 7 in the following shows parameter values which are assumed toperform evaluation on the SS block index indication.

TABLE 7 Parameter Value Carrier Frequency 2 GHz Channel Model CDL_C(delay scaling values: 300 ns) System Bandwidth 24 RBs Number of OFDMsymbol 2 symbols for PBCH REs for DMRS and Data 192 (96 × 2) for DMRS,384 (192 × 2) for Data Payload size 72 bits, 64 bits, 56 bits, 48 bitsPBCH TTI 80 ms SS burst set periodicity 20 ms PBCH Repetition 4 timeswithin PBCH TTI Subcarrier Spacing 15 kHz Antenna Configuration 2Tx &2Rx Transmission Scheme Time Domain Precoder Vector Switching (TD-PVS)Channel Estimation Non-ideal Modulation Order QPSK Coding Scheme TBCC

25. BWP (Bandwidth Part) for Transmitting Downlink Common Channel

An initial access procedure of LTE operates within a system bandwidthconfigured by MIB. And, PSS/SSS/PBCH is aligned on the basis of thecenter of the system bandwidth. And, a common search space is defined inthe system bandwidth, system information is forwarded by PDSCH assignedwithin the system bandwidth, and a RACH procedure for Msg 1/2/3/4operates within the system bandwidth.

Meanwhile, although NR system supports an operation in a broadband CC,it is very difficult to implement a UE capable of performing a necessaryoperation in all broadband CCs in the aspect of cost. Hence, it may bedifficult to implement the UE to smoothly perform an initial accessprocedure within a system bandwidth.

In order to solve the problem, as shown in FIG. 57, NR can define a BWPfor performing an initial access operation. In NR system, SS blocktransmission, system information forwarding, paging, and an initialaccess procedure for a RACH procedure can be performed within the BWPcorresponding to each UE. And, at least one downlink BWP can include aCORESET having a common search space in at least one primary componentcarrier.

Hence, at least one selected from the group consisting of RMSI, OSI,paging, and RACH message 2/4-related downlink control information istransmitted in the CORESET having a common search space. A downlink datachannel associated with the downlink control information can be assignedwithin a downlink BWP. And, a UE can anticipate that an SS block is tobe transmitted within a BWP corresponding to the UE.

In particular, in NR, at least one or more downlink BWPs can be used fortransmitting a downlink common channel. In this case, a signal capableof being included in the downlink common channel may correspond to an SSblock, CORESET having a common search space and RMSI, OSI, paging, PDSCHfor RACH message 2/4, and the like.

(1) Numerology

In NR, subcarrier spacing such as 15, 30, 60, and 120 kHz are used fortransmitting data. Hence, numerology for PDCCH and PDSCH within a BWPfor a downlink common channel can be selected from among numerologiesdefined for data transmission. For example, in a frequency range equalto or narrower than 6 GHz, at least one or more subcarrier spacing canbe selected from among 15 kHz, 30 kHz and 60 kHz subcarrier spacing. Ina frequency range ranging from 6 GHz to 52.6 GHz, at least one or moresubcarrier spacing can be selected from among 60 kHz and 120 kHzsubcarrier spacing.

However, in a frequency range equal to or narrower than 6 GHz,subcarrier spacing of 60 kHz is already defined for a URLLC service.Hence, the subcarrier spacing of 60 kHz is not appropriate fortransmitting PBCH in the frequency range equal to or narrower than 6GHz. Hence, in the frequency range equal to or narrower than 6 GHz, itmay use subcarrier spacing of 15 kHz or 30 kHz to transmit a downlinkcommon channel. In a frequency range equal to or wider than 6 GHz, itmay use subcarrier spacing of 60 kHz or 120 kHz.

Meanwhile, NR system supports subcarrier spacing of 15, 30, 120, and 240kHz to transmit an SS block. It may assume that the same subcarrierspacing is applied to an SS block, CORESET having a common search spaceand RMSI, paging, and a downlink channel such as PDSCH for RAR. Hence,if the assumption is applied, it is not necessary to define numerologyinformation in PBCH contents.

On the contrary, subcarrier spacing for a downlink control channel canbe changed. For example, when subcarrier spacing of 240 kHz is appliedto transmit an SS block in a frequency band equal to or wider than 6GHz, since the subcarrier spacing of 240 kHz is not defined for datatransmission, it is necessary to change the subcarrier spacing totransmit data. In particular, the SCS can be changed to transmit data.The change of the SCS can be indicated using 1-bit indicator in PBCHcontents. The 1-bit indicator can be comprehended as {15, 30 kHz} or{60, 120 kHz} according to a carrier frequency range. And, indicatedsubcarrier spacing can be regarded as reference numerology for an RBgrid.

(2) Bandwidth of BWP for Transmitting Downlink Common Channel

In NR system, it is not necessary for a bandwidth of a BWP for adownlink common channel to be identical to a system bandwidth on which anetwork operates. In particular, the bandwidth of the BWP may benarrower than the system bandwidth. In particular, the bandwidth shouldbe wider than a carrier minimum bandwidth but should be narrower than aUE minimum bandwidth.

In particular, in case of a BWP for transmitting a downlink commonchannel, it may be able to define a bandwidth of the BWP is to be widerthan a bandwidth of an SS block and is to be equal to or narrower than aspecific downlink bandwidth of all UEs capable of operating in eachfrequency range. For example, in a frequency range equal to or narrowerthan 6 GHz, a carrier minimum bandwidth is defined by 5 MHz and a UEminimum bandwidth can be assumed as 20 MHz. In this case, a bandwidth ofa downlink common channel can be defined in a range ranging from 5 MHzto 20 MHz.

(3) Bandwidth Configuration

FIG. 58 illustrates an example of configuring a bandwidth.

A UE attempts to detect a signal within a bandwidth of an SS block whilean initial synchronization procedure including cell ID detection andPBCH decoding is performed. Subsequently, the UE can continuouslyperform a next initial access procedure within a bandwidth for adownlink common channel. In particular, the UE obtains systeminformation and may be then able to perform a RACH procedure.

Meanwhile, an indicator indicating a relative frequency position betweena bandwidth for an SS block and a bandwidth for a downlink commonchannel can be defined in PBCH contents. In order to simplify theindication of the relative frequency position, a bandwidth for aplurality of SS blocks may correspond to a candidate position at whichan SS block is positioned within the bandwidth for the downlink commonchannel.

For example, assume that a bandwidth of an SS block corresponds to 5 MHzand a bandwidth of a downlink common channel corresponds to 20 MHz. Inthis case, in order to find out the SS block within the bandwidth forthe downlink common channel, it may be able to define 4 candidatepositions.

In NR system, it is not necessary for a bandwidth of a downlink commonchannel to be identical to a system bandwidth on which a networkoperates. In particular, the bandwidth may be narrower than the systembandwidth. In particular, the bandwidth of the downlink common channelshould be wider than a carrier minimum bandwidth but should be narrowerthan a UE minimum bandwidth. For example, in a frequency range equal toor narrower than 6 GHz, a carrier minimum bandwidth is defined by 5 MHzand a UE minimum bandwidth can be assumed as 20 MHz. In this case, abandwidth of a downlink common channel can be defined in a range rangingFrom 5 MHz to 20 MHz.

26. CORESET Configuration

(1) CORESET Information and RMSI Scheduling Information

It is more efficient for a network to transmit CORESET informationincluding RMSI scheduling information to a UE rather than directlyindicate scheduling information on RMSI. In particular, it may be ableto indicate frequency resource-related information such as CORESET, abandwidth for a frequency position, and the like in the PBCH contents.And, it may be able to additionally configure time resource-relatedinformation such as a start OFDM symbol duration, the number of OFDMsymbols, and the like to flexibly use a network resource.

And, a network can transmit information on a common search spacemonitoring period, duration, and offset to a UE to reduce UE detectioncomplexity.

Meanwhile, a transmission type and bundling can be fixed according toCORESET of a common search space. In this case, the transmission typecan be determined according to whether or not a transmission signal isinterleaved.

(2) Number of OFDM Symbols Included in Slot

In relation to the number of OFDM symbols included in a slot or acarrier frequency range equal to or narrower than 6 GHz, it may considertwo candidates such as a slot including 7 OFDM symbols and a slotincluding 14 OFDM symbols. If NR system determines to support the twotypes of slots for a carrier frequency range equal to or narrower than 6GHz, it is necessary to define a method of indicating a slot type todisplay a time resource of CORESET having a common search space.

(3) Bit Size of PBCH Contents

In order to indicate numerology, a bandwidth, and CORESET information inthe PBCH contents, as shown in table 8, it may be able to designateabout 14 bits.

TABLE 8 Bit size Details 6 GHz For a6 GHz Reference numerology [1] [1]Bandwidth for DL common channel, [3] [2] and SS block position # of OFDMsymbols in a Slot [1] 0 CORESET About [10] About [10] (Frequencyresource-bandwidth, location) (Time resource-starting OFDM symbol,Duration)  

 E Monitoring Periodicity, offset, duration) Total About [14]

indicates data missing or illegible when filed

(4) Measurement Result

A performance result according to a payload size (i.e., 48, 56, 64, and72 bits) is explained with reference to FIG. 59. In this case, assumethat 384 REs and 192 REs are used for DMRS. And, assume that aperiodicity of an SS burst set corresponds to 20 ms and a coded bit istransmitted within 80 ms. Decoding performance of PBCH according to MIBpayload size is shown in FIG. 59.

Referring to FIG. 59, if a payload size corresponds to maximum 72 bits,it is able to see that a performance requirement of NR-PBCH (i.e., 1%BLER in −6 dB SNR) can be satisfied using 384 REs for data and 192 REsfor a DMRS.

Referring to FIG. 60, a communication apparatus 6000 includes aprocessor 6010, a memory 6020, an RF module 6030, a display module 6040,and a User Interface (UI) module 6050.

The communication device 6000 is shown as having the configurationillustrated in FIG. 60, for the convenience of description. Some modulesmay be added to or omitted from the communication apparatus 6000. Inaddition, a module of the communication apparatus 6000 may be dividedinto more modules. The processor 6010 is configured to performoperations according to the embodiments of the present disclosuredescribed before with reference to the drawings. Specifically, fordetailed operations of the processor 6010, the descriptions of FIGS. 1to 59 may be referred to.

The memory 6020 is connected to the processor 6010 and stores anOperating System (OS), applications, program codes, data, etc. The RFmodule 6030, which is connected to the processor 6010, upconverts abaseband signal to an RF signal or downconverts an RF signal to abaseband signal. For this purpose, the RF module 1530 performsdigital-to-analog conversion, amplification, filtering, and frequencyupconversion or performs these processes reversely. The display module6040 is connected to the processor 6010 and displays various types ofinformation. The display module 6040 may be configured as, not limitedto, a known component such as a Liquid Crystal Display (LCD), a LightEmitting Diode (LED) display, and an Organic Light Emitting Diode (OLED)display. The UI module 6050 is connected to the processor 6010 and maybe configured with a combination of known user interfaces such as akeypad, a touch screen, etc.

The embodiments of the present invention described above arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It is obvious tothose skilled in the art that claims that are not explicitly cited ineach other in the appended claims may be presented in combination as anembodiment of the present invention or included as a new claim by asubsequent amendment after the application is filed.

A specific operation described as performed by a BS may be performed byan upper node of the BS. Namely, it is apparent that, in a networkcomprised of a plurality of network nodes including a BS, variousoperations performed for communication with a UE may be performed by theBS, or network nodes other than the BS. The term ‘BS’ may be replacedwith the term ‘fixed station’, ‘Node B’, ‘evolved Node B (eNode B oreNB)’, ‘Access Point (AP)’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to exemplaryembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit is located at the interior or exteriorof the processor and may transmit and receive data to and from theprocessor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of thedisclosure should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

INDUSTRIAL APPLICABILITY

Although a method of receiving a synchronization signal and an apparatustherefor are described centering on the example applied to 5^(th)generation NewRAT system, the method and the apparatus can be appliednot only to the 5^(th) generation NewRAT system but also to variouswireless communication systems.

1-14. (canceled)
 15. A method of receiving a synchronization signalblock (SSB) by a user equipment (UE) in a wireless communication system,the method comprising: receiving the SSB and a demodulation referencesignal (DMRS) for a physical broadcasting channel (PBCH), wherein theSSB includes a synchronization signal (SS) and the PBCH; and wherein asequence of the DMRS and a scrambling sequence of the PBCH are generatedbased on same bits for an index of the SSB.
 16. The method of claim 15,wherein 3 bits among 6 bits for the index of the SSB are obtained basedon the DMRS and remaining 3 bits are obtained based on a payload of thePBCH.
 17. The method of claim 15, wherein a number of the same bits isbased on a frequency band in which the UE operates.
 18. The method ofclaim 15, wherein the index of the SSB is related to one DMRS index. 19.The method of claim 15, wherein the sequence of the DMRS is generatedbased on a cell identifier for identifying a cell.
 20. A communicationdevice for receiving a synchronization signal block (SSB) in a wirelesscommunication system, the communication device comprising: a memory; anda processor connected with the memory; wherein the processor isconfigured to control to: receive the SSB and a demodulation referencesignal (DMRS) for a physical broadcasting channel (PBCH), wherein theSSB includes a synchronization signal (SS) and the PBCH; and wherein asequence of the DMRS and a scrambling sequence of the PBCH are generatedbased on same bits for an index of the SSB.
 21. The communication deviceof claim 20, wherein 3 bits among 6 bits for the index of the SSB areobtained based on the DMRS and remaining 3 bits are obtained based on apayload of the PBCH.
 22. The communication device of claim 20, wherein anumber of the same bits is based on a frequency band in which the UEoperates.
 23. The communication device of claim 20, wherein the index ofthe SSB is related to one DMRS index.
 24. The communication device ofclaim 20, wherein the sequence of the DMRS is generated based on a cellidentifier for identifying a cell.